4IO NEW YORK STATE MUSEUM 



know whether this abundance of hydras always occurs when the trout are 

 newly hatched. 



Two fine Diptera belong to the characteristic fauna of Little Clear 

 creek, but do not live in any of the situations we have been discussing. 

 These are the curious phantom fly, Bittacomorpha clavipes 

 Fabr., and our largest crane fly, Tip u la ab do min alis Say. Both 

 live almost out of the water in very shallow bays filled with red-rotted 

 vegetation and both are very common in such places. 



Gomphus scudderi Selys was common in the creek below the 

 wagon bridge, but was not taken above it. 



Part J 

 INSECT LIFE HISTORIES 



In the following pages there is assumed on the part of the reader such 

 a knowledge of the external parts of insects as is obtainable from the 

 elementary textbook of entomology or of zoology. He should know 

 that the body of an insect larva is composed of successive rings or joints; 

 that the first division is the head and bears the eyes, antennae and mouth 

 parts; the next three joints, bearing the wing and leg rudiments, con- 

 stitute the thorax; and the remaining joints, often with prop-legs or pro- 

 legs under them, constitute the abdomen. External gills are arranged in 

 delicate whitish tufts when in a sheltered position, or, when exposed, are 

 thin plates traversed by delicate air tubes. In addition to these, there 

 are at the sides of the abdomen, longer, paired, simple, pointed appen- 

 dages, called lateral filaments, which also, when small and delicate, may 

 serve the respiratory function. Lateral filaments, gills (with very few 

 exceptions) and prolegs disappear with the end of larval life, and are 

 absent in the adult insect. 



In the immature stages insects differ wonderfully ; but there are two 

 types of larvae, which have been distinguished by the degree of differ- 

 ence between larva and adult insect: i) those called nymphs, which 

 differ but litde from the adults in general organization, and when grown 

 transform directly to imagos, without having entered on a quiescent 

 pupal stage; and 2) larvae proper, which differ very greatly from their 

 imagos, having the adult appendages reduced in size or altogether 

 wanting, wings never visible externally, and requiring a quiescent pupal 

 stage, when they have done feeding, before transforming to the imago. 

 These two groups constitute the primary divisions of the table given 

 below. The student will find in Comstock's Manual for the study of 

 insects^ or in his Insect life^ or in a number of other books that are not so 



