Friday, 27 January 2017

Variation in Butterflies

Variation in butterflies is an interesting subject within the study of lepidoptera and there are a number of reasons for its occurrence. I am no scientist but broadly speaking, variation can occur as a result of the geographical isolation of populations which can lead to different sub-species and even new species evolving. Variation between the sexes (sexual dimorphism) and variation between different broods (seasonal dimorphism) occurs in many species. Variation (or aberrations) can also occur within a species as a result of genetic mutation or environmental influences during critical stages of the life cycle.   
I have seen numerous variations over the years and here is a selection of photographs.
Although the occurrence of some variants can be manipulated through captive breeding, the following examples were found and photographed in the wild.
Clouded Yellow (Colias croceus) (female)
The standard form.
Clouded Yellow (C.croceus) (female, form helice)
This pale form only occurs in the female of the species and can account for 10% of females.

Small Copper (Lycaena phlaeas) (female, form caeruleopunctata)
A regular form which displays a line of blue submarginal spots on the hindwings.

Small Copper (L.phlaeas) (male, ab. schmidtii)
This aberration is a genetic mutation caused by a recessive gene.

Common Blue (Polyommatus icarus) (male)
This species is sexually dimorphic.

Common Blue (P.icarus) (female)

Common Blue (P.icarus) (female, ab. albocincta)
Common Blue (P.icarus) (female, ab. supracaerulea)

Chalkhill Blue (Lysandra coridon) (male, ab. caeca)
All sub-marginal spotting is absent.

Chalkhill Blue (L.coridon) (female, ab. postobsoleta)
The female of this mating pair is showing much reduced sub-marginal spotting on the hindwing. 

Duke of Burgundy (Hamearis lucina) (female)
Not strictly regarded as an aberration, this specimen is displaying a pigment deformity in one wing.

White Admiral (Limenitis camilla) (female)

White Admiral (L.camilla) (ab. obliterae)
The reduced wing markings are caused by low temperatures during the pupal stage of the life cycle.

Small Tortoiseshell (Aglais urticae)

Small Tortoiseshell (A.urticae) (a transitional form of ab. semi-ichnusoides)
This aberration is caused by high temperatures during the pupal stage of the life cycle.

Comma (Polygonia c-album)

Comma (P.c-album) (ab. obscura)
The markings on the hind wings have become blotched and the borders are indistinct.

Wall (Lasiommata megera) (male)

Wall (L.megera) (male, ab. fascia)

Gatekeeper (Pyronia tithonus) (female)
Gatekeeper (P.tithonus) (female, ab. anticrasipuncta)
Many aberrations take the form of enlarged or reduced eye-spots.

Meadow Brown (Maniola jurtina) (male, ab. pallidus)
The normally chocolate brown ground colour has been replaced by pale grey and is not to be confused with age related bleaching that often occurs in this species

Saturday, 14 January 2017

Encounters with Hawkmoths

Hawkmoths are members of the Sphingidae group and they are amongst our most impressive moths, being large and fast flying. They are regularly attracted to light and I have recorded most of our resident species in my wealden garden over the years as well as two regular migrant species. Most Hawkmoth larvae are easily recognised by their large size and tail horns.
All photographs have been taken in my garden unless otherwise stated.

Convolvulus Hawkmoth (Agrius convolvuli) (female)
This is a scarce migrant from the European mainland but can be quite numerous in good migration years.
Privet Hawkmoth (Sphinx ligustri)

Privet Hawkmoth (S.ligustri) (larva on ash)
This specimen was found on the South Downs in East Sussex.

Pine Hawkmoth (Hyloicus pinastri)

Lime Hawkmoth (Mimas tiliae)

Lime Hawkmoth (M.tiliae) (larva found wandering)

Eyed Hawkmoth (Smerinthus ocellata)

Eyed Hawkmoth (S.ocellata) (larva found wandering)

Poplar Hawkmoth (Laothoe populi)

Poplar Hawkmoth (L.populi) (larva on sallow)
This specimen was found on the South Downs in East Sussex.

Hummingbird Hawkmoth (Macroglossum stellatarum)
This is a day-flying migrant from the European mainland and can be common in good migration years.

Hummingbird Hawkmoth (M.stellatarum)
In flight.
Elephant Hawkmoth (Deilephila elpenor)

Elephant Hawkmoth (D.elpenor) (larva on greater willowherb)
This specimen was found near Arlington in East Sussex but I occasionally find them in my garden.

Small Elephant Hawkmoth (Deilephila porcellus)
In Sussex, this species is predominantly found in downland habitats. I have recorded it only once in my garden. These two specimens were attracted to light in a Seaford garden.

Small Elephant Hawkmoth (D.porcellus)

Thursday, 12 January 2017

Winter Pursuits

Winter is a quiet time for the amateur entomologist but it is a good time of year to search for eggs of the Brown Hairstreak (Thecla betulae). The adult butterfly can be rather elusive during its flight season but if you know where to look, its eggs can be much easier to find. This species is a late season emergent and it is the eggs that see out the winter months on blackthorn, its foodplant. The eggs are usually laid singly (but sometimes two or three in a group), generally in the fork of a branch, near where the current and previous year's growth meet.
Brown Hairstreak (Thecla betulae) (ova on blackthorn)

When the winter sun is shining, then for me, there is no better place to go for a walk than on Ashdown Forest. I met up with Bob on Wednesday for a walk around one of our regular routes. I had never seen a Great Grey Shrike (Lanius excubitor) before, a scarce but regular winter visitor to UK shores. Whilst I could have seen one long before now, I just don't possess the "twitcher" gene and I have always been happy to wait for the moment when I would come across one when out for a walk. Well, that thrill happened for me yesterday when Bob spotted one sitting on top of a gorse bush. I managed to record the moment with this rather long distance shot.
Great Grey Shrike (Lanius excubitor)