On Larval Filamnets in the Eyed Hawk Moth

ON LARVAL FILAMENTS IN THE E Y E D HAWK MOTH.

127

ON LARVAL FILAMENTS IN THE E Y E D HAWK MOTH. BY

J O H N L . MOORE, B . A . ,

LL.B.

IN 1924 I reared a family of Smerinthus ocellatus, Linn., and the following notes on their life-history may be of interest. On the morning of 24th May a male and female, which had emerged from their pupae during the previous night, mated at about 8 a.m. They were parted at 2 p.m. on that day. The female commenced laying eggs about midday on the 31st May. She laid thirty-three eggs by 9.30 p.m. on that day, a further thirtyone by 9.30 p.m. on the Ist June, a further sixteen by the same time on the 2nd June, twenty-nine more by 8 a.m. on 3rd June and a further six by 1.30 p.m. on the 4th June. Although this number of eggs was not up to the usual capacity, she then seemed exhausted and I let her go. The first larvae emerged on the morning of the 19th June, and the whole hundred and fifteen were out by the morning of the 2Ist June ; so, although six days elapsed between the laying of the first and last eggs, all the larvae emerged within the space of forty-eight hours.

When first hatched, the young larvae clung very tightly to the food-plant by their hind claspers ; and when in their first skin, if dislodged from their position in the course of changing the food-plant or from any other cause, they suspended themselves by a filament that issued from the tip of the horn. After shedding their first skin, they no longer emitted this filament.

Therefore it would seem to be a provision of nature for enabling the larvae, if they should fall from their food-plant when very small, to recover their position with comparative ease; otherwise this they would be unable to do, owing to their diminutive size and the distance they would have to crawl, along the ground and up the trunk of the apple-tree upon which they would be feeding, in order to get back to the leaves. As they grow larger, their power of progression being more vigorous, this method of recovering their position would be no longer required ; hence they seem to lose the power of emitting the filament, the horn becoming a useless organ, like the human appendix although not so dangerous to life ! In fact, on several occasions larvae bit off the ends of each others horns, without any untoward result. This appeared to be a form of retaliation, when one larva got in the way of another on the leaves of the food-plant. Only twenty-eight larvae survived to the last skin, although they were kept in good healthy conditions and were free from the attacks of their natural enemies. Of

128

ON LARVAL F I L A M E N T S IN T H E E Y E D HAWK

MOTH.

this number, I retained fifteen and these pupated between the 5th and the 13th August.

Three of them made no attempt to burrow, but pupated on the surface of the earth, one of them taking five days from the 8th to the 13th August in the Operation.

The imagines all appeared between the 24th May and the 5th June, 1925.

[Mr. Moore's very exact and careful observations have brought to light an entirely new organ, hitherto unsuspected to exist among Sphingidcz.

It is unknown to both Mr. Robert Adkin, one of the oldest and most experienced of British lepidopterists, and the late J . W. T u t t ; the latter in his exhaustive ' British Lepidoptera ' iii, p. 433, says no more than that in its first larval Stadium Smerinthus ocellatus has " the caudal horn about onethird the length of the larva, appears black to the naked eye, but under a lens is seen to be deep pink, the black colour being due to the hairs ; " and at vol. iv, p. 473, adds only that *' the long caudal horn is of a red colour. The first moult takes place in two or three days."—ED.]

A N UNSEASONABLE B E E T L E . — O n e associates the Phytophagous beetle, Lochmcea cratcegi, Forster, so entirely with Mayblossom (and, in fact, I never remember to have met with it previously, except when beating such flowers) that it seems worth recording that I found a specimen crawling upon the wall of a boarding-house at Gorleston on 22nd September of this year.—C. G. DOUGHTY. [Our own series of specimens, from Suffolk and Sussex in 1894, was taken entirely during April and May ; Stephens' Manual of Brit. Coleoptera instances only May and June.

Its occurrence later is very exceptional; but Pearce found it to be ' abundant' at Dun wich in August 1920, and we took one at Lowestoft during September 1924.—ED.]