THEIR RELATION TO EACH OTHER 91 



genera and species remaining as representatives in 

 our fauna. All of them are feeders on animal matter 

 and most of them are predatory in all stages. The 

 best known forms are the scorpion flies, so called from 

 the curious anal appendages of the male, which bear a 

 remote resemblance to a scorpion tail without its ter- 

 minal sting. The larvae, which are somewhat caterpillar- 

 like, live under ground and prefer rather damp places. 

 There are not enough of the insects to make them of 

 any importance as checks to anything in particular, 



Fig. 38. — A Panorpa or scorpion fly and its larva. 



and as they feed rather indiscriminately on soft-bodied 

 insects, chiefly flies, they are of no economic value. 

 It is probable that this order represents the type from 

 which the Diptera and Hymenoptera were derived. 



The caddice flies or Trichoptera are aquatic in the 

 larval stages and as aerial adults do not feed at all. 

 As larvffi they derive their name from their habit of 

 making cases or "caddices" of various shapes from 

 little sticks or stones closely fitted and held together 

 with silk. Some of the species are feeders upon vege- 

 table matter, others appear to be predatory, or feeders 

 upon animal matter at least. They are very numerous 

 in specimens and species, but naturally do not influence 



