The aim of this project is to investigate how some insects, particularly moths and butterflies (order Lepidoptera), have become equipped for survival and reproduction in the Arctic. Arctic animals possess traits that help them to survive and reproduce under extraordinary circumstances (e.g. McAlpine 1964). If these traits have evolved due to selection pressure from the Arctic environment, including the predators and competitors that exist there, they are called adaptations. Adaptation makes an animal population better and better fitted (adapted) for life in the Arctic. It involves the evolution of new traits or the modification of old ones that facilitate life in the Arctic, and also the degeneration and eventual elimination of traits that are useless in the new habitat.

However, adaptation is usually a slow biological process, and it is possible that the relatively short time since the last glaciations (a few thousand years at most) has not been long enough for extensive adaptation in most animals (Strathdee & Bale 1998, Downes 1964). Therefore it seems likely that some animals managed to survive and reproduce in the Arctic because they happened to possess the necessary specializations right from the start. Such animals are not especially adapted to the Arctic, but may still survive and reproduce there because they have traits that they acquired elsewhere, before invading the Arctic. This is called ”preadaptation”.

In contrast to adaptation, dispersal and immigration by animals may be a very fast process, particularly for flying ones such as insects. It is therefore likely that many Arctic animal populations are relatively recent immigrants that manage to persist in the Arctic mainly thanks to preadaptation’s (i.e. essentially without true adaptations). These populations may run a high risk of extinction, but may have a good ability to recolonize.

On the Tundra Northwest 1999 expedition moths and butterflies were collected for the purpose of investigating if and how they possess adaptations particular to the Arctic environment, i.e. whether or not they differ from related forms living in other areas. As a by-product of our sampling efforts, we also carried out a faunistic survey of moths and butterflies in the areas visited, some of which were previously largely uninvestigated in this respect.

Butterfly and moth survey

Butterflies and moths (Lepidoptera) were collected whenever the weather permitted. These insects are common and spectacular components of most Arctic insect faunas, although they are usually only discernible in sunny weather. The moths and butterflies of the Canadian Arctic are poorly known in comparison with those of other Arctic areas, e.g. Greenland (Wolff 1964, Downes 1966). One purpose of the collecting was therefore to increase knowledge of the distribution of Lepidoptera in the Canadian Arctic. The following sites were visited:

l. Ungava, 1–2 July

The site was located on Cap de Nouvelle France, i. e. the northern tip of Ungava Peninsula. It was visited in very bad weather early in the season. Temperatures were around freezing, and the ground was snow-covered, so no butterflies or moths were seen at this site.

2. Melville Peninsula, 5–6 July

The site was on the eastern tip of the peninsula, near Cape Penhryn. The weather had become warm and sunny (max 16°C), and the first butterflies of the year were just emerging in large numbers. We caught adults of at least two species (Boloria polaris and B. frigga) and in addition larvae and pupae of several other species (including Colias nastes and Agriades glandon as well as the moth Gynaephora rossi).

3. Somerset Island, 9-10 July

This site was on a dry ridge just south of the Creswell River delta. The weather was warm and sunny (max l5°C), although very windy most of the time. Nevertheless we caught many recently emerged butterflies of at least two species (Bolaria polaris and B. chariclea), and also many moths (including Gynaephora rossi and G. groenlandica). It is very probable that several additional species also occurred at this site, but they may have passed undetected because they might still have been in the pupal stage. This is also the case for site 2 (on the Melville Peninsula). No butterflies or moths were previously known from any of these areas (Layberry et al. 1998).

4. Cornwallis Island, 12 July

We visited the village of Resolute Bay and the immediate surroundings for about two hours at midday. The weather was cool and cloudy (a few degrees above freezing). Only one moth (Psychophora sabinii) was found.

5. Bathurst Island, south, 13–14 July

This site was situated at ca. 100 m elevation somewhat inland from the south coast. The weather was warm and sunny (max l3°C) but windy on the first day, much cooler and even windier on the second. We found two species of moths (Psychophora sabinii and Gynaephora groenlandica) that occurred in abundance, but no butterflies. Only one species of moth (P. sabinii) was previously known to occur on this island (McAlpine 1964, Danks & Byers 1972).

6. Bathurst Island, north-east, 16 July

This site was on the north-eastern coast. It was visited for a few hours only and in bad weather. The temperature was around freezing and there was a strong wind. No butterflies or moths were seen.

7. King William Island, 20–21 July

The site was located near the western tip of the island, on a flat limestone plateau at sea level. It was rather rich in moths and butterflies. The weather was sunny part of the time and rather warm (max l2°C). The catch included one species of butterfly (Bolaria polaris) and three species of moths (Pararctica lapponica and Gynaephora spp., the latter occurred in very large numbers). King William Island seems to have been entirely unknown with respect to its butterfly and moth fauna (Layberry et al. 1998).

8. Victoria Island, 23–24 July

The site was located in an upland area (90 m) on the Wollaston Peninsula. It was relatively rich in plants and presumably also in insects. However, the weather had deteriorated and was cooler than at the previous site (max 7°C) and also very windy. Nevertheless, during a few hours of sunshine we managed to catch at least seven species of butterflies, including Bolaria (2 species), Oeneis (2 or 3 species), Erebia and Colias (2 species) and also a few moths that were active.

9. Paulatuk on the mainland, 26–27 July

The site was located on the sandstone plateau between Albert Bay and the Melville Hills, east of Paulatuk village. The weather was persistently foggy and cool (ca. 5°C), and moths and butterflies were largely inactive. We encountered only two butterfly (Boloria napea and Oeneis sp.) and two moth species.

10. Banks Island, 28–29 July

The site was located in a hilly area near the south coast, east of Sachs Harbour. It consisted of a rich tundra. Our visit appeared to coincide with the peak flight period for most species of Lepidoptera. The weather was windy but very warm and sunny (max 17°C) at least periodically. Moths and butterflies were incredibly abundant in same sheltered places, where they accumulated due to the wind. About a hundred specimens of fifteen different species were caught. Butterflies included Colias (2 or 3 species), Oeneis spp. (2 or 3 species), Erebia fasciata, Boloria spp. (3 species), Lycaena phleas, Agriades glandon and Erebia fasciata. We also caught many moths (including Grammia qvenseli and Gynaephora groenlandica, the latter occurred in enormous numbers; ca. 700 cocoons per hectare, which is the equivalent of about 1 kg of larvae earlier in the season).

11. Tuktuyaktuk, 31 July

A few hours’ stop-over at the airport in warm and sunny weather (ca 20°C) allowed us to capture a few specimens of each of two species of butterflies (Colias palaeno and Boloria chariclea) as well as one species of moth.

12. Inuvik, 1 August

A one day stop-over allowed us to catch same butterflies in and near the town and also along 60 km of the Dempster Highway south of it. The weather was very warm (ca 30°C) and partly sunny. However, the butterfly season was largely over at this site, so the species encountered were few (e.g. Limenitis arthemis, Nymphalis antiopa and Colias palaeno).

13. Thule Air Base, north Greenland, 2 August

During a half day (afternoon and evening) stop-over at Thule Air Base, we took the opportunity to collect butterflies and moths from the nearby hills. The weather was sunny and warm (ca l5°C), and for almost the first time during this trip (except at Inuvik), there was no wind and we could work in T-shirts! Butterflies (Colias hecla, Boloria chariclea and Agriades glandon; the three species known from this area) were very abundant, and we also observed some moths (including Entephria polata and Gynaephora groenlandica). In contrast to most of the Canadian sites, Thule is well known with respect to its insect fauna. The species we caught are all previously known from the area (Wolff 1964).

Altogether, we collected about 15 species of butterflies and 10 species of moths, same of which have yet to be identified as to species, altogether ca. 500 individuals. Many of our findings represent considerable range extensions for the species. The Lepidoptera survey will be summarized in a separate report as soon as the specimens are identified.

The flight periods of the various butterfly species in the Arctic vary considerably from year to year depending on the weather. In 1999 the early part of the summer was cool and cloudy over much of the Canadian Arctic, and the emergence of the butterflies was therefore probably much later than usual. The year to year variation in the flight periods may be substantial, and impossible to predict from the almanac. However, the butterfly emergence is probably closely related to the variation in the plant phenology. A first attempt was therefore made to set the flight period of the various butterfly species in relation to the phenology of same common tundra plants. The aim is to extend this effort to other Arctic areas in the future.

Butterfly wing coloration

The butterflies collected on the Tundra Northwest 1999 expedition will be used to test two hypotheses concerning the function of butterfly wing coloration. If butterfly wing coloration is adapted to the Arctic environment, we expect to find either of two trends: first, if the bright colours of many butterfly wings are signals aimed at insect eaters, carrying the message that the butterfly is unpalatable or otherwise not worth catching, we expect to find that the brightness (or the contrast) of butterfly wings decreases northwards. This is because the number of insectivorous birds, and hence the risk of being eaten, diminishes (Downes 1964). Second, if wing coloration serves a thermo-regulatory function, i.e. to increase the absorption of radiant heat from the sun, and thus facilitate flight performance, we expect the wings to be darker (dark absorbs more heat) in northern populations (Heinrich 1993). To evaluate these hypotheses the colours and contrast of the wings will be measured, using equipment available at Göteborg University. The Arctic butterflies will be compared across sites visited during Tundra Northwest 1999 and also with specimens native to warmer climates, i.e. sub-Arctic and boreal (mainland) Canada.

Ultrasonic hearing in moths

Most of this work was focused on the two exclusively Arctic moths, Gynaephora groenlandica and G. rossi of the family Lymantriidae and Psychophora sabinii of the family Geometridae. The three species occur side by side over most of the Canadian Arctic, sometimes in enormous numbers. In particular the big hairy larvae of the Gynaephora species are well-known. Larvae and cocoons (cover of silk protecting the pupa) were commonly found on the ground, although their density varied considerably from site to site. The cocoons were collected systematically, and brought back to the ship. Adult moths usually emerged within a few days, and virgin females thus reared were used to attract males in large numbers during subsequent stop-overs. In this way we collected good samples of Gyneaphora moths from most sites.

Like many other moths, lymantriids and geometrids are equipped with ultrasound detectors, i.e. simple ears located on the thorax (Lymantriidae) or on the abdomen (Geometridae). These ears are specializations used for detecting approaching bats, normally their major enemy (bats search for insects by means of high intensity ultrasound). Hearing an approaching bat triggers an evasive manoeuvre, which usually takes the moth to ”safety” on the ground.

Since they have ears, both Gynaephora spp. and Psychophora sabinii must have evolved in areas with bats in the first place, and only later invaded the Arctic. At present they occur only in the Arctic and on some mountains further south. So for these Arctic moths, which never experience any predation from bats, the ears are presumably completely useless. Hence, lengthy adaptation to the Arctic environment in these moths may be expected to result in the elimination of the evasive reaction and eventually also of the hearing.

We exposed moths to synthetic but bat-like ultrasound (26kHz) in short bursts and at high intensity and recorded their reactions. Gynaephora males were tested out in the field, as they flew towards pheromone-emitting females. Gynaephora females, which cannot fly with a full load of eggs, were tested in the field, as they emitted pheromones, and also in the lab on board the ship. Psychophora (males), of which we only had a few, were just tested on board the ship. Gynaephora males could hear the bat calls 15-25 m away, and the response always consisted of a rapid change in the flight direction away from the sound source (the bat). This is normal behaviour for lymantriids, so there was no indication that the evasive reaction or the hearing has been changed compared to other (non-Arctic) species (Cardone and Fullard 1988). Gynaephora females reacted by stopping the emission of pheromones for a second or so, as expected (Acharya & McNeil 1998), but in this case the behaviour differed considerably between individuals. Some could hear well (the bat call 15 m away), while others seemed to be almost deaf (could not hear it 0.5 m away). This indicates that hearing in the females is undergoing degeneration, but this could actually be a result of flightlessness rather than adaptation to the Arctic (non-flying moths are not exposed to bats either; Rydell et al. 1997). Psychophora sabinii males seem to hear less well than the Gynaephora males, and they do not show any well-defined evasive reactions. Hence, there is evidence for adaptation in Psychophora but not in Gynaephora.