172 THE ZOOLOGIST. 



scent is rather like that given off by Cockroaches."* "When a 

 Dytiscus is captured, it often discharges a milky fluid from the 

 thorax, just behind the head. The fluid smells like sulphuretted 

 hydrogen.f The Y-shaped " horn," which can be projected from 

 near the head of the larva of Papilio machaon, is the source of a 

 powerful odour of fennel — one of the food-plants of the cater- 

 pillar.t The scents emitted by insects cannot be always esti- 

 mated as of a " protective " character. Barrows and Schwarz 

 have stated that " it would seem that Crows have a predilection 

 for insects possessing a pungent or otherwise strong taste or 

 colour." This is exemplified by the prevalence of Garabidce 

 (among them the often-recurring genus Chlcenius possessing a 

 peculiar odour), coprophilous or necrophagous Coleoptera (Sil~ 

 phidce, Histeridte, and Scarabceida, Laparosticti), ants, and more 

 especially by the almost constant occurrence of certain species 

 of the heteropterous family Pentatomida. " It seems probable 

 that the strong odour or taste of these soldier bugs is the reason 

 why they are so eagerly sought by the Crows. "§ 



Gilbert White recorded an instance which appears to have a 

 " protective " explanation. " I knew a gentleman who kept a 

 tame snake, which was in its person as sweet as any animal while 

 in good humour and unalarmed ; but as soon as a stranger, or a 

 dog, or cat came in, it fell to hissing, and filled the room with 

 such nauseous effluvia as rendered it hardly supportable. "|| The 

 same author remarks that " odours also appear to serve among 

 animals as individual recognition signs. After ewes and lambs 

 are shorn, there is great confusion and bleating, neither the 

 dams nor the young being able to distinguish one another as 

 before. This embarrassment seems not so much to arise from 

 the loss of the fleece, which may occasion an alteration in their 

 appearance, as from the defect of that notus odor, discriminating 

 each individual personally ; which also is confounded by the 

 strong scent of the pitch and tar wherewith they are newly 



* Cf. Miall, ' Nat. Hist. Aquat. Ins.' p. 33. 

 \ Ibid. p. 61. 



% Fumeaux, 'Butterflies and Moths' (British), p. 140. 

 § 'Bull. No. 6, U.S. Dept. Agric, Div. Ornith. and Mamm., 1895.' Cf. 

 reprint in ' Indian Mus. Notes,' vol. iv. No. 2, pp. 86-91. 

 || ' Nat. Hist. Selborne,' Harting's edit. p. 86. 



