88 



The presence of three (and only three) pairs of jointed legs on 

 the body just behind the head will sei-ve to distinguish most in- 

 sect species at any stage of existence from members of the next 

 group (Crustacea), There are some exceptions to the rule among 

 aquatic larvae, suchas the abundant young of mosquitoes, of Chirono- 

 mus and Corethra; but larvse such as these may be recognized as 

 insects by the absence of jointed appendages on the divisions of 

 the abdomen, crustaceans differing^ in bearing, generally, such ap- 

 pendages, on most of the divisions of the body. 



An exhaustive treatment of the group in its relations to fish 

 culture would call for an account of every order of the class; for 

 while such orders as Hymenoptera and Lepidoptera are very largely 

 terrestrial, a glance at Prof. Forbes' most recent paper on the 

 food of fishes will shoAv that even bees, moths, and lepidopterous 

 larvae are devoured when chance brings them within reach. 

 Freshets surprise and carry into the current of streams great 

 numbers of terrestrial beetles and bugs which live in the 

 earth, under dead leaves, and on vegetation, and these furnish at 

 such times no inconsiderable part of the food of the smaller fishes. 



The common aquatic insects belong to the following orders 

 Diptera (flies), Coleoptera (beetles), Trichoptera (case fiies ), Neu- 

 roptera (hellgrammites, etc. ), Hemiptera (true bugs), Ephemeridse 

 ( May flies ), and Plecoptera and Odonata ( dragon flies ). Some of these 

 live in the water throughout life; others in the larval and pupal stages; 

 still others in the larval and mature stages; while a part are 

 aquatic only in the larval condition. The food varies greatly with 

 the species and may vary with different stages of the same insect. 

 It consists of decaying organic matter, or of living plants or animals, 

 while some forms constantly take a mixed aliment. It is not posr 

 sible therefore with our present knowledge of the subject to cal- 

 culate the effect of a sudden removal of the whole group from its 

 relations to the other life of our waters; but considered only as 

 fish food there can be no doubt that the effect would be decid- 

 edly to the detriment of fishes. Even those insects that prey 

 upon the eggs and young of fishes are themselves in turn de- 

 voured by the adult fishes, and there seem to be very few indeed 

 of the aquatic insects that are not eaten by fishes in greater or 

 smaller numbers. 



Order Diptera. (flies.) 



Adults with two naked wings and a pair of knobbed balancers. 

 Mouth parts elongated, horny or soft, fitted for taking liquid food. 

 Prothorax not free. Larva^ aquatic or terrestrial, without jointed 

 legs, with or without a developed head. Pupa commoidy inactive. 

 Examples: black flies, horse flies, gnats, and mosquitoes; larviv 

 known as wrigglers, maggots, and grubs. 



Flies of at least nine families are aquatic in the larval stage; but 

 the majority of the individuals commonlj' collected in our waters 

 pertain to the families, Simulidje, Culicida?, Chironomid{\3, and Ta- 



