The season 1998 offered a few interesting finds of migrants despite that the weather most of the summer was dominated by low:s from the Atlantic. June, July and August gave only few occasions with good conditions for incoming migrants. The comparably high number of finds made especially in June and September may have been due to the fact that the weather east of the Baltic region was warm over a vast area during large parts of the summer season. Firstly, this may in the beginning of the summer have caused the large influx of species like Plutella xylostella, Vanessa cardui and Vanessa atalanta. Secondly, the warm and for insects suitable weather in western Russia, Belorussia, Ukraine and large parts of SE Europe may also have allowed many of the migrating species to build up large populations closer to the Baltic region than normal. Herewith increasing the number of species that could reach Sweden in September from intermediate and short ranges. The extended use of light traps, especially in the south-eastern part of Sweden, has most probably also increased the percentage of incoming migrants that actually are observed. Moreover the greater awareness of the importance of weather conditions by Swedish lepidopterologists together with the report facilities on this home page have possibly further enlarged the interest for migrating lepidoptera. From introduction of the report system it has been possible to obtain information about different migration events almost instantly and thus allowing many lepidopterologists to respond within hours of the first reports of an event.
Some species like P. xylostella, V. cardui and V. atalanta turned up in numbers in southern and central Sweden already in the end of April and were thereafter more or less abundant throughout the season. Also in northern Sweden, these species were much more frequent than normal from second half of June until the end of the summer. Initially this was only due to a number of diffuse migration events, but towards the end of the summer an increasing proportion of the individuals seen were descendants who had hatched here. Other species like Nomophila noctuella and Autographa gamma came in more or less distinct waves. Noctuella first arrived in the end of April and was frequent the first weeks of May, thereafter there were some scattered finds throughout the summer until second week in September when a massive migration wave, culminating around the 20th, came. Gamma also came first in the end of April and was thereafter occasionally seen the first weeks of May, and in beginning of June came a new small wave to SE Sweden. Thereafter the species was hardly observed in Sweden until a huge wave reached southernmost Sweden last days of August. Thereafter gamma was the most common lepidopteran species on clover and alfalfa fields in southern and central Sweden throughout September.
Other species like Drepana binaria, Cyclophora porata and Mythimna albipuncta appeared under conditions indicating that most of the finds in 1998 came from native populations in Sweden. Most likely these populations were due to the large migrations of these species during previous years, especially in 1996.
On the 27th of April, a warm front reaches Sweden from south-east and on the 28th it sweeps up over southern and central Sweden. This front was generated by a low over central Europe but the transport of the warm air masses from Balkan were also enhanced by the high pressure over western Russia. These air masses brouth, as mentioned above, P. xylostella, N. noctuella, V. atalanta, V. cardui and A. gamma, and also Pieris brassicae, Phlogophora meticulosa and Agrotis ipsilon. Most finds were made on the Baltic island Öland, but also some scattered finds were made along the Swedish Baltic coast from Stockholm and southwards. Warm south-easterly winds prevail until the 2nd of May when a low over Denmark and Germany alters the wind direction to north east. During the following week, the dominating wind direction is various kinds of west. On the 10th a large high pressure over SE Europe brings up large warm air masses from southern Europe, which carry more noctuella, atalanta and cardui, but also Macdunnoughia confusa. In the following ten days, the weather is mainly dominated by high pressures allowing the immigrants to spread in Sweden. On the 19th a low over northern Scandinavia brings down cold air with north-westerly winds. The weather remains cold and wet with north-westerly winds until the 27th when a warm front reaches Sweden from south and the wind direction changes to S-SSE. A large high pressure ranging from eastern Poland to central western Russia brings up warm air masses to southern and south central Sweden that reaches their maximum expansion on the 30th. In these air masses came some V. cardui, large numbers of V. atalanta and A. gamma together with a migration wave of Pieris rapae. Other species that came during these days were Hyles galii and Macroglossum stellatarum from which one moth was seen in Getå (north of Norrköping) on the 30th of May. On Öland the peak of atalanta and gamma was the 2-3rd of June. Thereafter the weather in southern Sweden becomes less warm even though the prevailing wind direction remains south for another three days. During the coming week the weather in southern and south central Sweden remains relatively warm and stable with very warm air masses coming as close as the coastal areas of Poland and the Baltic republics. From the 10th of June the weather over Scandinavia is dominated by an Atlantic low, however, the warm air over the Baltic republics occasionally pushes westwards and reaches eastern- and southernmost parts of Sweden during the coming four days. In these warm spells come single migrants like an Agrius convolvuli which was found on Kullaberg (NW Skåne) on the 13th and a Pseudeustrotia candidula which was found in Västervik (NE Småland) the 10-13th. The weather in southern and south central Sweden continues to be dominated by lows and west winds coming in from the Atlantic until the second half of July. Occasionally in June warm air masses from the high pressure east of the Baltic republics reaches eastern Sweden. In northern Sweden warm air is occasionally driven up from east and south-east between the lows over southern Sweden and high pressures east of Finland and the Kola Peninsula. This weather pattern remains most of the time in northernmost Sweden between the 22nd of June until the end of July, thus producing a large number of days with nice warm weather and winds from east or south east. This wind pattern is most likely the reason for the unusually large number of observations of V. atalanta and V. cardui in the northern part of Sweden.
On the 21st of July a spell of very warm air masses from S-SE reaches southern Sweden, forced here by a large high pressure over SE Europe. These air masses were pushed eastward again within a day and are replaced with slightly less warm air coming up from the Iberian Peninsula and western France. Some weak fronts cool the weather to a minor extent in southern Sweden between the 22nd and the 23rd, but warm air is continuously coming up from SW. On the 24th a new warm front coming from south gradually raises the temperatures in southern Sweden again and thereafter slowly continues towards NE bringing warm weather along its track. During this period the high pressure from SE Europe is moving northwards and on the 27th it reaches the southern Baltic region and the wind direction changes to south-east in southern Sweden. The coming two days this high pressure continues towards north-east and the wind changes to S-SW in southernmost Sweden. During this period a number of migrants were found like: large amounts of H. galii on Öland and Västervik on the coast of Småland, a Catarhoe rubidata in Kämpinge (S Skåne) the 21st (it cannot be ruled out that it was of local origin), Cucullia fraudatrix one in Nybostrand, (E Ystad, S Skåne) 19-23rd and one near Lilla Frö on central Öland the 29th, one Orthonama obstipata in Uddevalla 24th (north of Gothenburg, P. meticulosa in Norberg (N Västmanland) the 25th, one Eilema griseola in the Sandhammaren (SE tip of Skåne) on the 27th and one Lithosia quadra in Hagestad (SE tip of Skåne) the 30th. The combination of having migrants (O. obstipata, P. meticulosa) coming with warm air masses from SW Europe in between periods of south easterly winds bringing migrants from eastern and south eastern Europe is very rare in Sweden.
On the 2nd of August the high pressure over eastern Europe reaches the Baltic region again, producing south easterly winds in the south eastern part of Sweden whereas the rest of the country is dominated by west winds. During the 3rd and the 4th the high pressure is gradually pressed towards NE by an incoming Atlantic low giving westerly winds also in SE Sweden. With the south-easterly winds came not only atalanta and cardui, but also Abrostola triplasia which were found on Öland the 3rd and the 4th of August. During the coming week a number of cold- and warm fronts driven by lows are dominating the weather in southern and central Sweden. On the 10th a small ridge of high pressure starts to build up over southern Scandinavia and northern Germany. In the coming three days the high pressure expands and gradually moves east to Estonia and southern Finland. From the 11th warm air masses are brought up over SE Sweden with south-easterly winds, whereas the winds on the Swedish west coast come from south and south-west. During the 13th the wind gradually changes to SW and then to NW towards the end of the coming day. In these warm air some migrants came like: Mythimna albipuncta from which 3 individuals were captured in the south eastern tip of Skåne between the 10th and the 18th; P. candidula were captured on northern Öland on the 14th; and the capture of a Schinia scutosa on central Öland on the 15th presumably originated from this migration wave. Thereafter the weather was dominated by lows, westerly winds and fronts until the 20th when a new warm front comes from west and the strong winds changes to SW over southern Sweden. With these winds came the first forebearers of the coming huge immigration wave of A. gamma, more atalanta and cardui and also Colias hyale from which one individual was captured in southernmost Skåne on the 20th. During the following three days the strong SW winds prevail, bringing in innumerable gamma to southern Sweden. Thereafter the wind changes to NW-NNW in southern Sweden as a result of the passage of a low over northern Scandinavia. This low dominates the weather with NW-NNW winds until the 31st of August. Despite the northerly winds A. convolvuli turns up on an island east of Oxelösund on the east coast on the 28th clearly showing that this powerful moth is able to migrate irrespective of wind direction. On the 30th three more were seen in Klinte on the Baltic island Gotland and some in Kalmar (on the coast of Småland) as well. One convolvuli from this migration wave was found as far north as the vicinity of Sundsvall in Medelpad in central Sweden. On the 31st a ridge of high pressure is starting to grow over central and northern Scandinavia between a vanishing low over Belorussia and a very deep low on the Atlantic west of the British Isles. On that day a M. stellatarum was observed in western Skåne. This high pressure grows until the 2nd of September and on the 1st and 2nd it produces NE winds over southern and central Sweden. On the 3rd 4th this high pressure slowly moves towards east, between this and the deep low which now has its centre over the English channel, warm air masses are brought up to most of southern Sweden with strong south-easterly winds. During the 5th 7th the same high pressure continues to grow and by now covers an area from southern Finland, the Baltic Republics to Ural and warm air masses from SE Europe are continuously pumped up over southern Sweden with the south-easterly winds. Despite the seemingly suitable weather only a few migrant species like: N. noctuella, A. gamma, a few finds of A. convolvuli (Eskilstuna and Trosa in Södermanland, on Öland, Axvall in Västergötland and Västervik in Småland) and Nycteola asiatica (S Skåne, W Blekinge), single finds of A. triplasia (S. of Stockholm) and Catocala nupta (S Halland; since this species is resident in southern Sweden it is difficult to distinguish between local finds and migrants) were reported during this period. During the 8th 9th the high pressure moves further south east to SE Belorussia and Ukraine and from the 9th the low between northern Scotland and Iceland shifts the wind direction to SW again bringing wet and cold weather over southern Sweden and so it remains until the 11th. On the night of the 8th the first migrants find their way to Uppsala, during this and the coming night N. noctuella, A. gamma (small ones), Xestia c-nigrum starts to appear in increasing numbers. Also Aplocera plagiata, M. confusa, Euxoa obelisca and a Noctua orbona (for the first time since 1987) were found in Uppsala. Surprisingly one Udea ferrugalis and three N. asiatica were captured east of Karlstad in Värmland north-east of lake Vänern on the 10th. On the evening the 11th the wind changes to SE-SSE because the high pressure moves from Ukraine towards north and central western Russia again. Warm air masses are once more pumped up to southern and south eastern Sweden from central and south-eastern Europe between the high pressure in the east and a low pressure over the British Isles. On the Swedish west coast air masses from SW Europe are pumped up by south winds (generated by the "British" low) at the same time. On Öland Margaritia sticticalis, N. asiatica, C. nupta (may be native), P. meticulosa, A. ipsilon and X. c-nigrum starts to appear that night. During the 12th and the 13th the weather and wind conditions remains approximately similar throughout southern Sweden. On the 12th more exotic migrants were seen, starting with a Colias croceus in Halmstad on the coast of southern Halland (SW Sweden). The same night a Rhodometra sacraria was captured in Halmstad as well and in Karlskrona in eastern Blekinge (SE Sweden) an Acherontia atropos was observed. On the 13th A. triplasia started to appear on Öland and Gotland and this species was hereafter found frequently on both islands until the end of September. A few finds of triplasia were made on the Baltic coast of Sweden like in Stora Vika south of Stockholm and the northernmost in Gävle on the coast of Gästrikland. On the 14th and the 15th the warm air masses transported by the south-easterly winds reached the entire Baltic coast as far as Hälsingland, whereas the west coast had south and later NW winds. On the 16th a minor low over SW Sweden and southern Norway turns the wind west again in southern Sweden, but the wind remains E-SE on the coast of Norrland. Within a few hours after the warm air had reached Uppsala on the 14th (NW of Stockholm) the first finds of Euchromius ocellea and N. asiatica were made. Altogether, two ocellea were found in Uppsala and one on Rådmansö on the coast of Uppland (north of Stockholm) where also one Udea ferrugalis was found this is the norhternmost find of this species in Sweden so far. However, asiatica continued to arrive in Uppland until the 21st giving a total capture of 17 individuals. Also to Krylbo in southern Dalarna (the 19th) one individual and to Årsunda (SW of Gävle) in the interiors of Gästrikland four individuals found their way. Also on Öland asiatica became frequent during this period and altogether 12 individuals were captured until the 27th. In Skåne another 12 were captured between the 13th and the 26th and on Gotland four were captured during the same period. Blekinge one more the 14th, central Småland one the 20th, 8 in Ljunghem central Västergötland the 15th, and one in Trosa, Södermanland the 22nd. During this period increasing numbers of A. convolvuli were found, most of them on Öland where approximately 60 were observed, but also in SE Skåne (3 individuals the 19-26th), W Blekinge (3 mid September), central Småland (10, the 15-18th), central Västergötland (1, the 18th), Gotland (4 ex second half of September), Södermanland (15, the 13-22nd) and northern Västmanland (1 the 19th). Other migrants that were found during these days were Palpita unionalis from which one was found on southernmost Gotland the 14-15th; one Chloroclystis v-ata was found in southern Halland the 15-19th; one Hyles livornica was found the 17th in Växjö in central- Småland; one Spodoptera exigua was found on central Öland the 20-25th; Helicoverpa armigera from which one was found on central Öland 12-14th and another the 16th, two more were captured on southern Gotland in the same period and one in Trosa Södermanland the 18th; four individuals of S. scutosa were captured on central Öland (one the 12th, two individuals 21st and one the 27th), one on southern Gotland between the 17th and the 27th and one in Axvall Västergötland on the 15th. Despite the modest number of U. ferrugalis found along the coast lines and on the Baltic Islands several inland finds were made during this period like in Västergötland, Ljunghem one each the 15th and the 17th, Axvall one the 25th and one in Flodafors in central Södermanland mid September. From the 11th and onwards there was a huge influx of X. c-nigrum which culminated the 22nd or the 23rd. Especially in Skåne and Halland the numbers were extremely high, but also on the Baltic Islands and along the Swedish east coast as far north as Uppland and Gästrikland this species was abundant.
On the 17th the low over western Sweden and southern Norway is further weakened and moves slowly towards east and the temperatures are somewhat lowered, but it is still much warmer that normal in southern and south central Sweden. On the 18th weak high pressure ridges over England-France, northern Scandinavia connects to a large high pressure over Ukraine. During the coming ten days (19-29) the weak high pressure is expanding over the entire NW Europe and spanning from the British Isles to Russia. Within this huge area the small pressure differences reduces the wind speed to a minimum producing weak winds of various directions, thus allowing the warm air masses, giving warm and sunny weather, to remain over southern Scandinavia. On the 23rd N-NNW winds are prevailing on the west coast, on the 24th the still a weak NW wind is prevailing on the west coast but in southernmost Sweden the direction is shifting to SE. During the day the 25th the wind changes to SSW along the west and south coast. Later that night and beginning of the 26th the wind changes to E and then in the coming day to SE over the entire southern Sweden, the wind mainly remains SE-E for the coming two three days.
A more concentrated spell of migrants appeared on the west coast from the 21st and during the following days. On the 21st U. ferrugalis and A. triplasia, started to appear in southern Halland and a C. v-ata was found in Uddevalla in central Bohuslän. A few C. nupta occurred in southern Halland on the 22nd. The 23rd three N. asiatica were found on three different sites in southern Halland and one in central part of this district, together with other migrants like U. ferrugalis, N. noctuella, P. meticulosa and X. c-nigrum. Surprisingly the main wind direction over the west coast the 23rd was a weak NNW, either this means that the asiatica:s were pressed south from the inland or rather that the wind pattern was more complex than can be superficially seen from the weather maps. The same night a single find of asiatica was also made in Ljunghem in central Västergötland, indicating that it most likely was a migration wave from east reaching western Sweden this day (cf. the dates above). Together with N. noctuella, Lymantria monacha, P. meticulosa and A. ipsilon the last asiatica was seen on the 26th in southern Halland making a total capture of 5 during these 5 days. Also on the Baltic Islands several C. nupta were observed during this week and one was found as far north as Häverö on the coast of Uppland the 26th. During the period 18-27th a pyralid moth, Synclera traducalis, was captured in a light trap on southern Gotland. This species has once been found in Bulgaria, but this was the first find of the species in northern Europe. This species mainly occurs in tropical Africa and in the Central East where its distribution is less well known. The 26th a Luperina zollikoferi was found in eastern Skåne together with the last N. asiatica and in the coming days the number of migrants observed decreased strongly despite the seemingly favourable weather. The origin of S. traducalis and L. zollikoferi is difficult to detect. The air masses bringing them to Sweden originated from the Mediterranean region and were brought eastwards on the southern side of a large low covering central Europe. Then the warm air masses were pushed over eastern and south-eastern Europe where they were turned towards the Baltic region. L. zollikoferi is assumed to come from central Asia but this does not fit with the air movements, but perhaps a migration wave of this species came in air masses from east that mixed themselves with the Mediterranean air somewhere over eastern Europe. Such an event could also explain the simultaneous finds of L. zollikoferi in southern Finland.
On the 28-29th an Atlantic low is passing over southern Scandinavia gradually deteriorating the warm weather over NV Europe and on the 29th the wind gradually changes to NE over the Baltic sea as the low passes towards east. From the 1st of October the weather goes back to "normal" and the wind to west as the lows from the Atlantic starts to rule again. Most of October west winds prevail and several Atlantic storms pass southern Sweden during the month and the season seems to come to an early and wet end since no more warm air masses find their way to the north. Despite this, some Peridroma saucia found their way to south eastern Skåne (one 23-31st of October and two 7-13th of November), showing that migration may occur also during apparently unsuitable conditions and that the very late part of the season may also yield interesting finds.
All names are according to the checklist "The Lepidoptera of Europe" by Karsholt and Razowski 1996.
Nils Ryrholm, Department of Animal Ecology, Evolutionary Biology
Centre, Uppsala University, Norbyvägen 18 D, S-752 36 Uppsala,
Sweden
Nils Ryrholm, Dept. of Zoology, Uppsala university, Villavägen 9, S-752 36 Uppsala
The season 1997 never reached the same lepidopterological magnitude as the remarkable summers of 1995 and 1996. However, even if this season was less impressive than the previous two, clearly it was one of the best ever for migrating lepidoptera. This season, as the previous ones, did not start too well since spring (March May) was much colder than normal. After a warm spell first week in June, the weather became cooler until the end of the month. In the last days of June, the summer both tourists and entomologists were hoping for arrived! In southern and central Sweden (including the southern mountain range) it was the warmest summer ever recorded! This is quite impressive since the data ranges back about 250 years from some sites. For instance, Stockholm had a mean temperature in August 97 which was more than five degrees warmer than average! This corresponds approximately to the August means of Budapest! Due to the high number of rainstorms, most areas of Sweden never became dry. This was the first warm summer without drought in Sweden I have ever experienced. Unfortunately the summer in southern Sweden ended abruptly the 6th of September. Thereafter, the autumn became cooler than normal which presumably killed off the progeny for several southern expansion species. There has been a strong tendency in the last ten years that the climate in Sweden has become a bit more continental, not only with warm summers but also cooler springs and autumns.
This season was in a sense remarkable since several of the mainly most common migrants, e.g. Plutella xylostella, Nomophila noctuella and Vanessa cardui, were more or less lacking throughout the season or only occasionally found in small numbers. Also Autographa gamma was lacking most of the season, however, there was a vast influx the last weeks of August and the first days of September.
The first presumed migrant for the season was Vanessa atalanta, of which a few individuals were seen in Skåne and Halland already in May. However, since May was unusually cold and unsuitable for migration, it cannot be ruled out that these individuals had hibernated in Sweden.
The next observed migrants, a number of Vanessa atalanta and a few V. cardui were surprisingly reported from the mountains of Jämtland in the western part of central Sweden. These butterflies were observed 3-10th of June when flying over the tundra heath. It is strange that no other observations of these species have been made in the same period! A few more V. cardui were observed along the coast of Södermanland (south of Stockholm) the last days in June. They arrived together with the warm air from the south.
During the first half of July, several individuals of Pseudeustrotia candidula were captured on southernmost part of the Baltic island Gotland (two 5th, one 6th and one 10th of July). During the same period, some candidula´s were found also on the Baltic island Öland (6th of July) and the corresponding part of the Stockholm archipelago (1st of July). One Itame loricaria was captured on the island Stora Karlsö (west of Gotland) on the 13th of July. In July, tree Eulithis pyropata (one each the 8th, 15th and the 21st) were captured on southern Gotland. The species is presumably established on Gotland, but the captured moths may nevertheless have been migrants. In the same area, Cryptocala chardinyi was captured as new to Sweden on the 23rd of July. On Öland, two Colobochyla salicalis were captured in July. The first one was captured on the 1-2nd and the other on the 18th, these were the first finds in Sweden since 1977!
Towards the end of July, Phyllonorycter pastorella was found as confirmed new to Sweden in the NW fringes of Stockholm. Just afterwards, the species was found on the coast of Uppland, north of Stockholm, and thereafter it has been found on several other sites in this region as well. Obviously this species is expanding its range dramatically at the moment. Most likely these finds are descendants from an earlier migration wave from Finland where the species is rapidly expanding.
Macroglossum stellatarum were recorded at least six times in Sweden in 1997. The first one was seen south east of Gävle in mid July. Ronny Lindman, who has had several traumatic experiences with this species during the past years, learnt to master stellatarum this year. He captured three individuals, which is half of the records for Sweden in 1997! The first one on the 30th of June, the second on the 12th of July and the third the 27th of August was captured on light. All finds were made in Southern Halland. One more stellatarum was taken on light in the beginning of September in SE Skåne. I believe that those were the first ones have been captured on light in Sweden. One more stellatarum was observed the 23rd of September in Southern Halland.
Despite the sunny weather in the second half of July and first week of August, the conditions for long distance migration into Sweden never became really suitable. Only a few odd finds on odd localities in southernmost Sweden like: Perizoma sagittata, Oncocera semirubella and Crambus pascuella (all the 21st in SE Skåne), Thaumetopoea pinivora (one the 22nd on southern Öland and one individual each on the 1st and 2nd of August in SE Skåne), Lymantria dispar (four individuals 23-30th on Öland), Crambus silvella (six individuals the 27th in SE Skåne), Vanessa atalanta (a few the 29th in SE Skåne) Eilema griseola (one individual each on the 2nd and 3rd of August in SE Skåne), Neustrotia candidula (one the 3rd on the coast of E Småland), Cucullia artemisiae (one the 7-9th in SE Skåne) and again Lymantria dispar (one the 7th in E Blekinge), were probably mainly due to immigration.
Throughout August, Lithosia quadra appeared on Öland and Gotland in such numbers and under such conditions that it is likely that the species is established there nowadays and it was therefore impossible to detect an eventual migration of this species to the Baltic islands. Equally, Watsonalla binaria, Cyclophora porata and Araschnia levana were resident at least in Skåne this year and therefore it was not possible to trace eventual migrating individuals. Perhaps binaria also has become resident on southernmost Öland, the find of eight comparably smaller moths between the 13th and the 16th of August indicates this. However, the finds of porata on Öland in August, the 22nd, the 23rd (two ex) and the 31st, are most likely results of migration.
Despite the incredible weather in August, the number of interesting finds in the middle of the month were relatively low. As a portend on what to come, a Schinia scutosa was found on northern Öland the 13th and another one in southernmost Skåne the 16-18th. Other finds this period were: Lymantria dispar (one the 14th and one the 25th on Öland), Eilema griseola (one the 15-18th on the coast of E Småland) and Neustrotia candidula (two the 16th and one the 24th on Öland). Nevertheless, when turning into the second half of the month the number of interesting finds increased, starting with observations of 16 Colias croceus in Skåne the 15-21st. On the 19th, a Danaus chrysippus was observed by birdwatchers near Falsterbo in SW Skåne. This was the first observation of this species in Sweden. However, the basic assumption must be that is a fugitive from a butterfly garden since there are no other observations of this species from NW Europe this year. During these days, massive swarms of Autographa gamma arrived, which became the most abundant moth species (after being practically absent the entire summer) virtually overnight. On the 22nd of August, there was almost a mass occurrence of Agriphila poliellus in westernmost Blekinge. This species has been declining dramatically in Sweden and is regularly found (in low numbers) only within this region. Whether they were of local origin or migrants is unclear. It is noticeable that the moths only could be found on this spot during this night and not again later. Also a single find was made close to Malmö in SW Skåne the 27th, which indicates that the observed moths were primarily migrants. The 23rd-25th a new migration wave of Colias croceus reached Skåne and approximately 25 individuals were seen. On the 25th the only Swedish Hydraecia ultima from 1997 was found on northern Öland. On the 27th of August, a huge influx of Colias croceus came to Öland. Between the 27th and the 31st approximately 80 butterflies were seen. Including the observations from Skåne and a few stray finds, the total count in Sweden for 1997 is more than 120, which is the highest number ever recorded in Sweden for one season! While searching for croceus, it was found that Scinia scutosa was flying in a low proportion of in the immense swarms of Autographa gamma which were inundating the alfalfa fields on Öland. The number of scutosa increased the first days of September with the peak 4-6th, thereafter the warm air currents ceased. During these days another 30 - 40 scutosa:s were recorded from Skåne, Halland, Öland, Gotland, Södermanland, Uppland and Gästrikland (northernmost record in Sweden). The total capture of scutosa in 1997 is approximately, which is the largest number ever recorded in Sweden and presumably these records almost doubles the total number of finds in Sweden. The warm SE currents also brought a Catocala adultera to Uppland in the end of August and some dozens Agrius convolvuli to SE Sweden, one each of Mythimna albipuncta to Öland and Gotland (both the 27th of August), one Nycteola asiatica to W Blekinge (the 29th), one Palpita unionalis to SE Skåne (1st of September), one Mesogona oxalina to the coast of Södermanland (south of Stockholm, the 2nd) and some Spodoptera exigua to: Öland (one the 2nd), Östergötland (one the 4th) and Gotland (seven) first days of September. Presumably as a result of the large influx in August - September 1996, there was a resident population of Mythimna albipuncta in southern Skåne this year.
In the beginning of the second week of September, the warm summer was abruptly replaced by an unusually cold autumn spoiling most fieldwork plans. However, in the period 13-23 September, there were a spell of SE and S winds, bringing up not very warm, but at least slightly warmer air. Among the species recorded from this period were: two Luperina zollikoferi one in Stockholm and one on Gotland on the 15-16th (first record in Sweden since 1984), two exigua on Öland one on the 13th and one on the 21st; approximately 25 individuals of convolvuli scattered over Sweden, the northernmost ones found as far north as in Västerbotten; a handful Udea ferrugalis in SE Skåne, one Peridroma saucia in Skåne; one Helicoverpa armigera on Gotland and last but not least a Chrysodeixis chalcites on the 22nd as new to Sweden. The moth was captured in a light trap in the Stockholm archipelago.
October did not bring much except autumn-depressions in 1997. The only migrants found this month was two Agrius convolvuli the 11th of October in NW Skåne. Thereafter the season slowly faded away in drizzle and fog not giving any further opportunities for long distance migration. As an illustration of the warmth deserting the Nordic countries, the last Vanessa atalanta were seen on their way south in SE Skåne on the 13th of October.
All names are according to the checklist "The Lepidoptera of Europe" by Karsholt and Razowski 1996.
Nils Ryrholm, Department of Animal Ecology, Evolutionary
Biology Centre, Uppsala University, Norbyvägen 18 D, S-752
36 Uppsala, Sweden
All names are according to the new check list "The Lepidoptera of Europe" by Karsholt and Razowski 1996. Names of Macrolepidoptera are marked in bold.
After the season 1995, most lepidopterologists in Sweden thought they would never experience something similar. This view was proven wrong already in 1996 which turned out to be an even more remarkable year!
The first migrants, mainly Plutella xylostella, came with a south-eastern hot spell starting 22-23rd of April lasting for a few more days. In the following month, P. xylostella was the most frequent species, especially in the northern half of Sweden.
At the end of May and beginning of June, a new hot spell came from south-east lasting approximately one week. The warm air mass brought another wave of Plutella xylostella and immense numbers of Vanessa cardui and Autographa gamma to the south-eastern part of Sweden. The number of V. cardui in June was possibly the highest ever recorded in Sweden. The individuals of these three species spread themselves throughout the entire country the following month and were seen in numbers even as far as in northernmost Sweden. A. gamma, for instance was the most frequent Noctuid species in the mountains of Härjedalen (central Sweden) in mid June and the species has never before been recorded in such numbers in this region. The only infrequent migrant species found during this period were Heliothis peltigera from which one specimen was captured the 8th of June in southern Halland on the Swedish SW coast; and one Macroglossum stellatarum which was captured at sunset the 11th in SE Småland, SE Sweden.
Then came a period of weather mainly unfavourable for both lepidopterologists and migrants which lasted for slightly more than a month in SE Sweden and increasingly longer further north. However, one H. peltigera was recorded in SE Skåne the 26th of June.
Around the 20th of July a high pressure zone started to bring warm air from the south-east to the Baltic islands of Gotland and Öland and to some extent to the adjacent coastline of SE Sweden. The first migrants found were a few Callimorpha dominula which were captured on the 20th on the coast south of Åhus in NE Skåne. Approximately 25 km north-east of Åhus in Sölvesborg, western Blekinge, two more dominula were recorded on the 23rd and 27th. At the same site in Sölvesborg one Blastobasis decolorella, a species new to Sweden, was found as on the 25th. Whether this moth came as a migrant or has been introduced is presently not known. Within a few days of this Nomophila noctuella, M. stellatarum, Eilema griseola, and Lithosia quadra had all been recorded on Öland. The highlight of this week was one Trichoplusia ni found on the 27th on Öland. This record was the first of the species in Sweden (for more detailed information about Öland, see Betzholz et al. in the "News*" page). During the same week a Cucullia artemisiae was recorded, however, it is unclear if this was a migrant or part of a newly established population. In the following two weeks, individuals of L. quadra were regularly found throughout Öland. Syngrapha interrogationis also appeared as a migrant on Öland during this period. On the coast of Södermanland, south of Stockholm a number of very small, migrating individuals of Malacosoma neustria were recorded during the last days of July and at the beginning of August. This small form of neustria type was also found at the same time in eastern Småland as well as on Öland and Gotland, indicating a massive migration into Sweden of this species.
This weather system then grew in over entire Fennoscandia and produced predominantly warm weather from the end of July until the end of August (throughout the whole country!). In the very south the warm weather prevailed until the beginning of September. The prevailing wind direction during most of this period was SE in the southern half of Sweden. Occasionally the wind came from the east or south but rarely from the west, thus producing more or less excellent migration conditions over more than 30 consecutive days.
In Skåne and Blekinge, in southernmost Sweden, the weather gradually turned warm from 25-27 July. Towards the end of the month, after two or three days of warm southerly winds, the first foreign moth species were recorded. As forbearers of what was to come, N. noctuella and large numbers of A. gamma appeared. The comparably small influx of N. noctuella continued throughout August. Among the migrating gamma:s were a high proportion of small individuals of the "gammina" type. In the three last days of July came a Cryphia domestica plus a wave of Lymantria dispar (only males recorded) and the first specimen in Sweden of Idaea ochrata was found in SE Skåne. In the first days of August a few Drepana binaria and Cyclophora porata were recorded in SW Skåne. On the 12th of August, one specimen of Melantria procellata was captured for the first time in Sweden in SW Skåne. During the 13-20th of August the wind turned more to the east and hence the number of migrants found in Skåne were reduced. However, one Eilema palliatella the first confirmed find in Sweden, a few L. quadra and Scinia scutosa (14th and 16th) found their way to Skåne during this period.
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The more easterly wind direction brought large numbers of migrants to the Baltic islands Öland and Gotland. Between the 9th and the 18th Oncocera semirubella, E. griseola, L. quadra, Autographa mandarina, Hydraecia ultima and Noctua janthina were captured on Gotland; and on Öland O. semirubella, L. dispar, E. griseola, L. quadra, Catocala nupta, A. mandarina, H. ultima, Cucullia fraudatrix, S. scutosa and N. janthina were caught during the same period.
On the eastern coast of the mainland of southern Sweden a number of migrants such as: O. semirubella, Pelosia muscerda, L. quadra, C. domestica, A. mandarina, Abrostola triplasia and H. ultima were found during that week.
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| Trichoplusia ni, Libanon 1955 | Idaea ochrata, Sweden, Ö.Hoby 28 July - 1 August 1996 |
The E and SE wind systems prevailing in beginning to mid August also facilitated northward migration within Sweden. Such events are very hard to detect due to the similarities in fauna, but during these extraordinary favourable conditions a number of species from southern Sweden were recorded for the first time far north (approximately 900 km) of their normal range. For instance Phycita roborella, Aplocera preformata and Campaea margaritata were found, along with a number of zoogeographically less remarkable species. In some cases individuals of these species were found on tundra habitats in the mountains! Also in August the numbers of A. gamma in northern Sweden were higher than average, further, N. noctuella were found from mid - end of August as far north as Gävle in central Sweden. In this area one Orthonama obstipata was found last week of August, which, together with a find from 1995, is the northernmost record in Sweden
Around the 20th of August the main wind direction over Skåne changed to the south, whereas it remained predominantly south-easterly in SE Sweden and on the Baltic Islands. This produced a weather situation that brought migrants to Sweden from two directions.
An influx of Mythimna albipuncta into Skåne started on the 21-23rd with four finds in the SW - and three in the SE corner. In SE one S. scutosa and the first two Spodoptera exigua specimens were recorded the 23rd with large numbers of A. gamma, mainly "gammina" type, and a few N. noctuella. In this and previous week, at least four Chortodes brevilinea were captured at one site in SW Skåne, but presumably these moths came from a newly established local population. In the same period (20 - 27th) a number of Colias croceus were observed in the SW, as well as two in SE Skåne the 21st. During the same period in SE Skåne an increasing number of M. albipuncta were recorded as well as approximately a dozen individuals of each D. binaria and C. porata. Whether the two latter species have resident populations or not in this area is presently unknown. On the 27th the first Swedish record of Cryphia algae was made in SW Skåne. On the same date a H. peltigera was captured in Halmstad, Halland on the Swedish SW, one of the few finds made on the west coast during the summer season. The number of albipuncta finds in SE Skåne continued to grow throughout August and well into September.
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| Melantria procellata, Austria, Steinmark | Cryphia algae, Germany, Mittel Rein |
The prevailing easterly wind on Öland and Gotland continued to bring in more O. semirubella and L. quadra until the 26th of August when the influx of these species apparently stopped. From the 23rd and the week thereafter, Euchromius ocellea, S. exigua and Euxoa obelisca started to appear in increasing numbers on both islands. On Öland a handful of each ocellea and exigua were captured, moreover a few Agrius convolvuli and a Pseudoeustrotia candidula. On Gotland there was a distinct wave of S. exigua coming in at early morning the 26th, at which time also one Hyles euphorbiae was captured, and a second wave of exigua arrived a few days later. The night after a Pyralis regalis was found together with the last L. quadra. During the last hectic days of favourable weather on Gotland more S. exigua, but also Hypomecis punctinalis, Nycteola. asiatica, C. nupta, H. ultima and Heliothis armigera were recorded.
The total record of S.exigua on Gotland was between 35 and 40, which taken together with the finds on Öland and the ones captured in Blekinge, Skåne, Småland and Uppland, indicate that this was the largest influx of S. exigua into Sweden since the mass migration in 1964! Also the influx of L. quadra is presumably one of, if not, the largest ever in Sweden, with a total score of approximately 100 specimens from 7 districts.
Simultaneously on the adjacent Swedish mainland O. semirubella, E. ocellea, A. convolvuli, L. quadra, Thaumetopoea pinivora, N. asiatica, H. ultima, S. exigua and a Prodotis stolida were recorded. The peak flights in the Stockholm area appears to have been 27-29th of August. The stolida specimen was found in SE Småland, at a shopping centre and therefore it is unclear if got there by its own or by other means of transport. In the vicinity of Västerås one exigua was captured on the 29th and another on the 1st of September. These are the only inland records of exigua in 1996.
Almost exactly on the last day of August came a cold spell from the north that closed the fiesta all the way down to south-central Sweden. After the first of September the warmth only remained in Skåne.
Here the number of M. albipuncta continued to grow until almost mid September when the weather became too unfavourable for any activities of this species. However, the last lingering laggard was caught as late as the 28-30th of September. Altogether approximately 30 specimens were captured in southern Skåne, most of them in the south-east. This number of records roughly doubles the total score of this species in Sweden! The remarkable occurrence of albipuncta in Skåne corresponds well with the appearance of the species in Denmark at the same time. The moths may at least partly have hatched as close as Denmark, since the number of observations has increased there the last years. In western Blekinge one S. exigua was captured on the 29th. As mentioned above a few S. exigua, but also some E. ocellea found their way to SE Skåne during the last days in August and first days of September when also two H. peltigera were captured. In the second week of September there came a short hot spell from the south which resulted in the capture of a few Udea ferrugalis, the first Peridroma saucia and some A. convolvuli in SE Skåne.
From mid September autumn had full command over the whole of Sweden, and thus the migration activities ceased almost completely. Despite the unfavourable weather a M. stellatarum was observed outside Gävle the 16th of September and an O. obstipata was recorded at the end of September on Gotland.
At the beginning of October the weather in southernmost Sweden gradually became warmer and around the 10th warm Mediterranean air reached Skåne on warm S and SSW currents. In the following week the warm air masses slowly expanded towards the north and about five to seven days later the air mass reached its northernmost position, covering at bit more than the southern third of the country. Thereafter the air mass began to slowly retreat southwards again and, despite a minor northward warm push some days earlier, the cold weather reached Skåne again towards the end of first complete week in November. Hence gradually closing the migration season of 1996!
In the city of Malmö, SW Skåne, one M. stellatarum was found on a wall on the 6th of October. In the beginning of this month the number of finds of P. saucia were rising day by day in southern Skåne. Immediately after the arrival of the warmth after the 10th saucia started to appear in numbers in the southern half of Skåne, but a few finds were also made in adjacent districts. In S Halland there was a peak on the 14-16th , in SW Skåne the peak was 12-20th and in SE Skåne the peak was roughly between the 20th and 25th. The pattern of the records indicate that the major influx of saucia came from south west, which is also corroborated by the finds in Denmark. One saucia was captured in western Blekinge (north-east of Skåne) on the 19th which well fits in with the general pattern. Also Xylena exsoleta, Agrotis ipsilon were distinctly more abundant in October than average, whereas A. segetum was less common. Between the 16th and the 18th a Palpita unionalis, a few O. obstipata and one H. armigera were found in SE Skåne. In the following week a E. ocellea, a few more O. obstipata and one Lithophane semibrunnea, new to Sweden, were found in SE Skåne. The record of semibrunnea corresponds well with the migration movements of the species in Denmark at that time. In Nybro, Småland one O. obstipata was captured on the 8th and in Halmstad, Halland one more was captured on the 20th.
When the warm air reached Öland on the 14th and over the following six days O. obstipata, N. asiatica and P. saucia were found, whereas on Gotland and the Swedish mainland no conspicuous records were made during this period. The last spell of warmer weather of the year reached Öland and Gotland in beginning of November. This resulted in the capture of one O. obstipata and one P. saucia on Öland, with one U. ferrugalis, two O. obstipata and one P. saucia recorded at the same time on Gotland.
In Skåne the influx of P. saucia continued until the last warm air mass was expelled in November. The total record of saucia in the autumn 1996 was more than 50 specimens, thus doubling the number of finds of this species in Sweden.
In conclusion one might say that 1996 was a year that will be hard to outshine, but, bearing in mind what was thought after 1995's season it is hard to conceive what future seasons may bring.
1997-02-22
Nils Ryrholm, Dept. of Zoology, Uppsala university, Villavägen 9, S-752 36 Uppsala
Nils
RyrholmThe season 1995 was presumably the best year for migrating lepidoptera ever recorded in Sweden. In beginning of June there came a hot spell from the Caucasus region. These atmospheric conditions gave us about 10 days of excellent weather, in which enormous amounts of Plutella xylostellacame. The descendants of these migrants "polluted" Sweden for the rest of the season, even in the very north where this species was the most abundant moth in July. In same spell large numbers of Vannessa cardui and Nomophila noctuella came as well. A few Macroglossum stellatarum were also observed. In Finland, this weather prevailed until beginning of July so they had an even greater party with dozens of Macroglossums there, which also produced a second brood. This offspring also spilled over to Sweden in August - October, with a few observations in the eastern part of the country. In mid July there came a short spell from SE, bringing Lithosia quadra, Eilema griseola, Protochinia scutosa and some other species to the Baltic islands. In beginning of August southerly winds prevailed for a week bringing Drepana binaria, Cyclophora porata, Cucullia fraudatrix, Protochinia scutosa, Photedes brevilinea (new to Sweden) and Autographa mandarina to Skåne (southernmost Sweden). In the beginning of September the party accelerated again when a weather pattern built up a almost three week continuos transport of warm air from Caucasus. In this period about a hundred Nycteola asiatica was captured (and the same numbers in Denmark, the previous total capture in Sweden is slightly more than 20), several hundred Udea ferrugalis (previous total capture in Sweden approx. 40), approximately a hundred Euchronomus ocellea (previous total capture in Sweden approx. 15), one Palpita unionalis, about a dozen Protochinia scutosa, three Heliothis armigera (one captured in Sweden before), ten Laphygma exigua, one Mythimna albipuncta, one Acherontia atropos, a bunch of Agrius convolvuli, five Ortonama obstipata and strangely enough several dozens of Lithophane consocia. All captures were made in eastern Sweden. Then we got two weeks of rest before a weather system producing SW winds arrived in the beginning of October. This weather pattern prevailed for three weeks. In that period Nephopterherix angustella, Mythimna unipuncta, Schrankia intermedialis (might be an overseen native) and Hypena lividalis all were observed in Sweden for the first time. Other interesting finds were Vitula edmanii, Peridroma saucia and some further Udea ferugalis. Besides these finds several interesting observations of the local fauna were made. All finds were in southernmost part of Sweden.
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| Photedes brevilinea Sweden, Sk. Löderup Aug. 1995 | Agrius convolvuli, Sweden, Sm. Kalmar 10 September 1995. |
Nils Ryrholm, Dept. of Zoology, Uppsala university, Villavägen 9, S-752 36 Uppsala
Nils.Ryrholm