MEANS OF DEFENCE OF LARV.1-. 45 



shadow on the leaf, and thus leading to the detection 

 of the larvae. Obviously larvae which live on trees 

 cannot so readily escape by dropping to the ground as 

 those attached to low plants. In fact they seldom or 

 never drop down ; many of them too feed only at night, 

 but the species of Nematus can defend themselves by 

 whipping about the abdomen. This is a habit pos- 

 sessed by all those which feed on the edge of the leaf, 

 but it is more noticeable with gregarious species like 

 Croesus septentrionalis. Grass and herbage-feeding 

 species again feed on the underside of the leaf on broad- 

 leaved plants, or along the edge of grasses, and they 

 drop to the ground at once, remaining there motion- 

 less rolled up in a ball until they think danger is over. 

 Species of Taxonus and Tenthredo afford examples of 

 this habit. 



The active means of defence consist in ejecting 

 liquids from lateral pores, or from the mouth, or 

 in giving off odours from glands (generally abdo- 

 minal). The Cimbicina possess the first mentioned 

 peculiarity. The liquid is of an acid nature, and it can 

 be ejected to a considerable distance and in some 

 quantity, although after three or four discharges the 

 supply becomes exhausted for a time. Its principal 

 use is no doubt against ichneumons, and this, in at 

 least one case, is the purpose of the liquid ejected from 

 the mouth. The larva of Perga Lewisii, for instance, 

 can throw out to some distance a quantity of gummy 

 matter, the use of which is clearly shown by an 

 ichneumon having been found with its wings and legs 

 gummed together by it. 



Larvae which give out secretions or fetid odours are 

 gregarious, several feeding on the same leaf, often 

 ranged in a row with the bodies stuck out in the air. 

 They have nearly always bright colours ; the ground 

 colour, as a rule, is some tinge of green, or even blue, 

 and the first and last segments are yellow or orange, 

 while the rest of the body is ornamented with yellow 

 and black spots which often end in stiff hairs. The 



