1906.] 267 



DRILUS FLAVESCENS, Rossi, ?, AND ITS LARVA. 

 BY E. G. BAYFOSD. 



On the evening of September 2nd, 1905, my friend, Mr. A. 

 Wbitaker, who had just returned from a holiday which he had been 

 enjoying at Deal in the company of Mr. Gr. T. Porritt, gave me a 

 curious larva which he had found whilst looking for bats in a cave on 

 Folkestone Warren, The following day I examined it more closely, 

 and by the aid of the description given by Westwood (Int. Modern 

 Class. Insects, I , p. 253) I determined it as that of Drilasflavescens. 

 To corroborate this I went out in search of Helix nemoraJis, and was 

 not long in finding a specimen, which, along with the larva, I placed 

 under a small bell-glass. The larva, which was very active, became 

 strongly excited on discovering the presence of the Helix^ and, 

 making a sudden rush upon it, quickly mounted the shell. Its action 

 was precisely that of a cat after a stealthy approach towards a bird 

 which it has marked down for its prey — one excited rush decides the 

 event. Bending round the shell it quickly made an entrance by in- 

 serting the head and two or three following segments at the base of 

 the columella. The Helix realising its danger at once withdrew 

 into its shell, drawing in with it still more of the larva. Quickly 

 emerging it attempted to thrust out its enemy, but was powerless to 

 do so. It repeated these tactics several times, but each time it with- 

 drew the larva pressed in still further. At last it gave up the struggle 

 and remained in its shell. Meanwhile the larva had set to work 

 devouring its victim, the juices of which could be seen quite clearly 

 through the transparent integument passing down the gullet. Whilst 

 watching the strenuous exertions of both parties in the combat I was 

 struck with the great advantages, both o:ffensive and defensive, which 

 the possession of the setigerous tubercles gives the larva. So far as I 

 can learn there is no adequate description of the larva. In Canon 

 Fowler's " British Coleoptera " the description is obviously condensed 

 from Westwood {I.e.) to which, indeed, the student is referred. 

 Since the publication of the former work an excellent " Life History 

 of Drilus Jiavescens, by Mr. L. E.. Crawshay, M.A., Oxon," has 

 appeared in the Trans. Ent. Soc, 1903, pp. 39 — 51, with two plates. 

 Although I had determined my larva by the aid of Westwood's 

 description, the latter is so inaccurate that I drew up another as 

 complete as I possibly could without injuring my specimen. As a 

 consequence I have laid more stress on the obvious features of which 

 Mr. Crawshay has treated lightly, and perforce omitted the more 

 minute but none the less important structural peculiarities which he 

 has so fully described. 



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