Skinner, Such trees were almost absent above the m contour, doubtless explaining the apparent altitude limit. However, there was a narrow zone of overlap with filigrammaria where scattered birches grew amongst old heather on one part of the site. Captive rearing Although the flight periods of the two taxa were well-separated in the wild, environmental factors might have been responsible. Would the difference be maintained if both were reared side by side, on the same food plant and under identical conditions?
In an attempt to answer this question, captive rearing was undertaken in This also gave the opportunity to compare larval coloration and markings. Eggs Eggs were obtained from two female filigrammaria found on fence posts at the site on 22 and 24 August They were laid singly or occasionally in groups of two or three on the stems and twigs of Heather. When newly laid the eggs were cream and conspicuous, but after a few days they became reddish-brown and much harder to see. They overwintered in this state.
Eggs were also obtained from a female autumnata found freshly emerged under birch at the site on 28 October and subsequently mated. They were laid singly or in small clusters on the lichened twigs of birch.
When newly laid, the eggs were pale greenish-blue, thus differing from those of filigrammaria. After ten days to a fortnight they likewise changed to reddish-brown and were no longer distinguishable. Both sets of eggs were kept in separate containers placed side by side in an unheated outbuilding over the winter, giving some protection from predators and frost but otherwise exposing them to outside temperatures and humidity.
As spring approached they were checked daily. The eggs of filigrammaria hatched from March , while the eggs of autumnata hatched from April It seems strange that the eggs of the more upland species were the earlier to hatch. A possible explanation is that its main foodplant, heather, is evergreen and would be available at any date, whereas the deciduous trees preferred by autumnata are not in leaf until later. Majerus, Thus the well-known differences between larvae of filigrammaria and autumnata Porter, could be triggered in this way, heather being a much darker green than the young leaves of deciduous trees such as birch.
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In an attempt to rule out any such effect, I reared a dozen larvae of each species on an identical foodplant directly from hatching. Because filigrammaria eggs hatched so early in the spring, only the young leaves of hawthorn Crataegus monogyna were available. Surprising, the newly hatched larvae thrived on this unfamiliar diet, suffering fewer losses than those offered heather.
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Larvae of autumnata also accepted hawthorn readily. Both species were reared in similar containers under natural light and outside temperature conditions. Other larvae of both species were reared on their more usual foodplants.eatharbarce.tk
Heather, bell heather, bilberry and eared sallow Salix aurita were all accepted by filigrammaria , while autumnata was given birch. With hindsight, the opportunity to try it on heathers was missed. No correlation was found between diet and larval coloration. Larvae of filigrammaria were identical whether reared throughout on hawthorn or on heathers, bilberry and sallow, maintaining their distinctive coloration and pattern.
Larvae of autumnata were identical whether reared on hawthorn or birch. First instar larvae of both filigrammaria and autumnata were very similar, being dark olive-green with black head and prolegs. However, differences were already apparent by the second instar. Larvae of filigrammaria remained dark olive-green and already showed signs of a yellow sub-dorsal line and paler spots; the head was dark grey-green. Larvae of autumnata were now paler, being yellowish-green with lighter longitudinal striations, the sub-dorsal line being no more prominent than the rest; the head was yellow.
In subsequent instars, these differences increased. Larvae of filigrammaria varied from mid-green to a dark, almost blackish-green, though with an almost white ventral surface. The unbroken, bright yellow sub-dorsal line was always their most striking feature, together with the yellow pinnacula; the yellow spiracular line was often weak or broken centrally, being strongest on the thoracic and rear abdominal segments. The head was mid-green, flushed with brown on the darkest individuals. Instead, the paler longitudinal striations were of even width and strength, making the white or yellowish spiracular line the main feature.
The white or yellowish pinnacula were small and inconspicuous. The head was yellowish-green to green, never with a brownish flush. Emergence Pupae were left undisturbed in their cocoons, spun in peat and moss. Both containers were placed side by side in an unheated outbuilding under identical conditions, and checked daily from mid-August onwards.
The first autumnata emerged on 25 September and the last on 5 November , giving an even wider spread. Thus the timing of the emergence of the reared moths was similar to that observed in the wild, although the separation of the flight periods was not quite so clear-cut. In particular, the first autumnata emerged eight days earlier than any wild sightings, giving an overlap with filigrammaria of three days. Nevertheless, the findings show that the much earlier flight period of filigrammaria is not simply due to environmental factors such as altitude and temperature.
Conclusions At the study site, filigrammaria and autumnata undoubtedly behaved as two distinct species. They showed major differences in flight period, foodplant and habitat, despite some overlap in distribution on the site. Whether such a clear separation is maintained throughout their ranges in Britain, and whether filigrammaria is indeed absent from continental Europe, are matters that should be investigated.
DNA analysis is another obvious line of enquiry. Acknowledgements I thank my neighbours, Ron and Sheilah Runcie and the Addisons, for allowing me access to their land at all hours of the day and night.
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References Karsholt, O. The Lepidoptera of Europe. Apollo Books.
Majerus, M. The New Naturalist Moths. Porter, J. The colour identification guide to Caterpillars of the British Isles. Skinner, B. The colour identification guide to Moths of the British Isles. Skou, R, Nordens Malere. South, R. Moths of the British Isles. Waring, P. British Wildlife Publishing. Partial second brood of Lomaspilis marginata L. In contrast, my first record this year of L.
Normally single-brooded flying June and July mid May onwards in the south , L. Peter Davey, the Dorset vice-county macro-moth recorder, informs me there is no record of a partial second brood of L. Variation in British moths, but not the butterflies, has been a neglected aspect of interest and study for over one hundred years. The species is now much less common. Until recently, numbers seen at mv light or at sallow blossom have been prolific and only estimates of the numbers of individuals of the various forms have been made; with many forms identification is not possible by quick cursory examination.
Of this species a number of generalizations may be made.
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It is remarkably variable, especially regarding basic coloration, and what Tutt refers to as the central shade on the forewing is a constant character, although obscured in very dark specimens. Pale hind wings are a rarity. In south-east England, blackish forms tend to be predominant; in Scotland reddish forms are common.
There is evidence of industrial melanism, but it appears to have been little studied, a remark which also applies to geographic variation. In view of the paucity of information and lack of named illustrations in modern textbooks on British moths, I have added a brief description for each form mentioned. I have only used the term aberration for the occasional rarity which is not a regular component of a local mixed population.
Listed below are the forms found in north-west Kent comprising those noted at my garden mv light at Dartford and those seen on the North Downs at Eynsford, varieties seen in the woodlands in East Kent and those encountered, mainly at sallow blossom, in the Highlands of Scotland. At Dartford several dark, unicolorous forms have predominated. Glossy, deep black and f. These two appear to be the forms most likely to be industrial melanics, but decline in melanism at Dartford remains slight.
Collins , Larger Moths of Surrey, , comments that mottled forms are commonest on the heaths and intensely black specimens are regular in south London. L less observed in rural East Kent than at Dartford. These comments suggest industrial melanism in the London area. Of regular occurrence at Dartford, it is very much less common than several other forms.
The hindwings are grey gradually darkening to become a darker border, similar to those of the two previous forms-listed. It is almost impossible to detect any trace of the dark central shade eve on thirty year old cabinet specimens. The hindwings may be uniformly dark or whitish with a dark grey border. It is not uncommon in north-west Kent and I have specimens from Dartford and Eynsford.