THE GUM SAW FLY. 117 



CHAPTER LVIIL 



THE GUM SAW FLY. 



{Perga dorsalis^ Leach?) 



Order : Hymeno-ptera. Family : Tenthridinidce. 



This insect, which is the largest and most common of 

 our Victorian saw flies, will no doubt be familiar to all 

 who either live in or travel in the bush by the singular 

 larvae which will be found huddled together on leaves of 

 young gums, which they rapidly destroy. The larvae, as 

 many as twenty or more, may be found both on the upper 

 and underside of the leaves, also on the upper part of 

 stem of the saplings, upon which they feed, arranged for 

 the most part in regular rows. When disturbed, and 

 especially if touched, they bend their bodies in the form 

 of an arch, and emit a greenish fluid from the mouth ; 

 they also emit so powerful an odour of the leaves as to 

 scent the room they may have been placed in for obser- 

 vation. When full grown (see Fig. I., which shows the 

 grubs at work on the leaves) they are about 2^ inches 

 in length, of a uniform velvety black, with numerous 

 short stiff" white hairs, and with six large reddish feet, 

 apparently being destitute of the fleshy pro-legs so com- 

 mon in the larvffi of Tenthridinidse. When feedino- thev 

 keep the abdominal portion of their bodies in motion, 

 rapping their extremities against the leaves. They bury 

 themselves under the ground, forming brownish cocoons 

 (see Fig. TI., which are reduced in size) of a very strong 

 texture, and from which the perfect insect emerges. 

 When newly out of the cocoons the fly is very soft and 



