IO 



THE ORGANS OF INSECTS 



species i.e. Hydropsyche guttata with the 

 various nervures and spaces between them 

 named. The student will be well advised to 

 master the details shown, as constant references 

 are made to them in systems of classification. 

 (Fig. i.) 



The Legs. The leg is divided into five parts the coxa 

 or hip, the trochanter, 1 the femur or thigh, the 

 tibia or shank, and the tarsus or foot. The 

 tarsus consists of one to five segments, and 

 terminates in either one or two claws called 

 ungues, between which is a pad called the pul- 

 villus. In some genera of the Hydropsy chidce, 

 in the male, the outer claw is malformed or 

 is replaced by a tuft of strong hairs, the claws of 

 the female being normal. The pulvillus is some- 

 times regarded as a sixth segment of the tarsus. 



Th spurs. I* 1 many Orders and Families, the legs are 

 furnished with spurs as well as spines and 

 hairs. The former are usually of a greater 

 transparency than the latter, and their arrange- 

 ment and number are of such importance 

 in the determination of the TRICHOPTERA 

 that I have detailed them in a special table 

 on p. 20. 



The The abdomen as a general rule is composed 



Abdomen. o f ten segments, and contains the more import - 



1 There is a doubt as to whether the trochdnter should be 

 termed a separate division, some writers considering it merely 

 a subdivision of the coxa. In certain genera of the EPHEMERID^E 

 the legs are atrophied and the joints formless. These insects 

 must pass the whole of their adult life in the air, the metamor- 

 phosis from the sub-imago to the imago stage taking place 

 whilst in flight. 



