3IO Insects and their Surroundings 



male becomes winged and leads an active life in the 

 open air. 



Inquilines. — A number of insects instead of actually 

 devouring others, feed at their expense. Many Gall- 

 flies do not themselves produce galls, but lay their 

 eggs in the galls already formed by the activity of 

 other members of their family. The nests of bees 

 and wasps serve as a home for numbers of such 

 " cuckoo-parasites." Some, like the grubs of the Oil- 

 beetles, eat the stored -up honey ; others, like the 

 caterpillars of certain Pyralid moths, devour the comb; 

 others again, like the maggots of Volucella, a genus 

 of two-winged Flies, act as scavengers. Ants' nests 

 are tenanted by many species of small Beetles, Aphids 

 and Scale-insects, which do scavenging work for the 

 ants or supply them with luxuries in the shape of sweet 

 secretions. Hence they render service for the shelter 

 and food provided by their hosts, and must be re- 

 garded as more honourable inquilines than those which 

 take to their own or their offsprings' use the labours 

 of others without making any return. 



Abnormal Feeders. — It is of special interest to 

 notice instances where insects abandon the method of 

 feeding usual in their families to strike out fresh lines 

 for themselves. It has just been mentioned that the 

 grubs of certain Gall-flies live as inquilines in the 

 galls of others. Within the same family are found 

 insects which lay their eggs in the bodies of plant- 

 lice or fly-maggots, their grubs living as parasites. 

 The great family of the Ground-beetles (Carabidae) 

 are normally carnivorous, yet many of the species 

 occasionally, and some habitually, take to a vegetable 

 diet and devour roots. Caddis-worms are almost 

 all plant-eaters, but the Hydropsychidae devour 

 insects and sometimes practise cannibalism. No 

 insects are so typically vegetable-feeding as the 



