76 Mr. P. Cameron 07i the 



highest phase of this protective coloration ; for not only do 

 its larvfe have a bad smell, and are covered with a resinous 

 secretion, but they resemble very closely the droppings of 

 a bird."^ Dineura stilata and D. degeeri aflbrd other 

 instances. I am strongly inclined to believe that the 

 obscure coloration of these protected larvae has been 

 acquired as a protection against ichneumons, by rendering 

 them less conspicuous, while the secretions have been 

 acquired against the attacks of carnivorous insects. Flat 

 larvce like those of Eriocampa cannot defend themselves 

 with the abdomen like those which feed along the edge of 

 the leaf, as I have already explained. It is worthy of 

 remark that the Eriocampa and Dineura larvae are not 

 always exhaling the odour, but only when danger is near. 



It may be noted here that the habit of congregating 

 together on the upper or lower surface of the leaf, and 

 eating only the epidermis, is not confined to saw-fly larva;. 

 We have a very good illustration of it with Phratora 

 vitellines, the beetle whose larvie are so common on willows. 

 And the reason of it is obvious. A large, gaudily-coloured 

 larva might live apart, and be still easily observed ; but 

 the only way small larvae can make their presence known 

 is by massing together. 



III. On Parthenogenesis in the Tenthkedinid^. 



The first indication of the occurrence of Parthenogenesis 

 with the Tentliredinidce, was recorded by a gardener 

 named Thorn, f who had observed Nemattcs ribesii to 

 deposit fertile eggs without having had any access to males. 

 This observation remained unverified until 1866, when 

 Kessler, a German naturalist, confirmed it.| The same 

 species formed the subject of many careful and extended 

 experiments by Von Sieboldg — experiments which proved 

 beyond all doubt that Parthenogenesis was a common 

 phenomenon with this saw-fly ; and that only males were 

 produced out of the unfertilised eggs. 



Last year I experimented with N. ribesii, and had no 

 difiiculty in getting several females to lay eggs without 



* As remarked by Jordan, Ent. M. Mag., viii., 252. 



t Gardener s Magazine, vii.,196. 



J Die Lebensgeschichte von Centoi'liynchus sulcicollis imd Nematns 

 ventricosus. Cassel, 1866. 



§ Beitr. zur Parthenogenesis der Artbropoden. Leipzig, 1871, pp. 

 106—130. 



