196 Mr. P. Cameron on the. 



do not form regular lines. The markings are usually 

 black and orange, and often fore and aft the body is 

 orange or yellow. Instead of keeping their bodies close 

 to the leaf and following its outline they stick them out 

 into the air, so that they assume the form of a U, the 

 turned-up tail reaching to the head and frequently above 

 it. Some of them bear black marks on the belly, between 

 the ventral legs, and also glands, which they can protrude 

 at will, and from which exude a foetid odour. To make 

 them even more conspicuous, several of them feed on the 

 same leaf, while they keep the posterior part of the body 

 in a state of continual agitation. Most of them are im- 

 eaten by birds, and they are also proof against the attacks 

 of insects, for a cockroach would not eat some larvre of 

 Nematus pavidiis with Avhich I supplied it, after having 

 subjected it to a fast of some days, Avhile it devoured 

 those of iV. niiliaris. 



I think that the habit these insects have of whipping 

 the body about is not so much to frighten birds as to 

 intimidate ichneumons from depositing eggs in their 

 bodies. I once observed a TrypJion endeavouring to lay 

 its eggs in some larvge of Croesus septentrionalis, which 

 at that time were very common on an alder bush. It 

 tried it on several larvjB. In one case five larvjB were on 

 the same leaf, aiid Avhenever the parasite approached them 

 in a moment they were in a state of considerable agitation, 

 and the intruder was driven away by the active lashing of 

 their bodies. It, however, succeeded with a solitary larva 

 which was rather inactive, being apparently about to 

 moult. I may here remark, that every saw^-fly larva which 

 I have found "stung," i.e. with ichneumon eggs on its 

 body, had them invariably on the fore region of the body, 

 generally on the thorax, frequently even on the head — a 

 circumstance readily understood when we consider that 

 the posterior part of the body can be easily moved away, 

 while the anterior part can only be removed by the creature 

 letting go its hold of the leaf. The only way it can do 

 this with sufficient swiftness to escape the ovipositor 

 of the ichneumon is by dropping to the ground at once. 

 And this we find to be the case with many larva?, especially 

 with those attached to grasses and other low-growing 

 plants, e.g., the larvfe of Dolerus, Tentliredo, Avhich drop 

 down on the slightest occasion. On the other hand, larvte 

 attached to trees do not readily drop down, but then we 

 have seen that some of them can protect themselves by 



