THE CANADtAN ENTOMOLOGIST. 



341 



the thorax, make in all ten pairs. I have not attempted to deter- 

 mine Whether the lateral spiracles are closed or not. 



Arising from the under side of the last segment is a pair of 

 light coloured cerci, cylindrical, soft and flexible, measuring .0 mm. 

 in length. The function of these cerci is not known, unless they 

 serve to aid the larva in maintaining itself on the surface film when 

 it requires a fresh supply of air. 



The legs are long, of the same colour as the head, and well 

 fitted for walking or running. The femora of all three pairs of 

 legs are also provided with swimming fringes. The larvae, how- 

 ever, are not very capable swimmers, only swimming short dis- 

 tances between supports. 



The mature larva. — (Fig. 30.) The larva ready to pupate 

 measures 40 mm. (P/ie ins.) long and about 9 mm. wide at its 



widest part. It is 

 dark brown in col- 

 our, the head be- 

 ing reddish brown. 

 The under surface 

 of the body is al- 

 m o s t a grayish 

 brown. The legs 

 are the same col- 

 our as the head. 

 Extending from 

 the anterior mar- 

 gin of the thorax 

 on each side of the median line to the tip of the abdomen is an 

 irregular narrow grayish brown line. These lines stand out 

 prominently in alcoholic specimens. 



The head is large, depressed, reddish brown in colour with 

 numerous darker markings. It is not out of proportion to the rest of 

 the body, as in the case of the young larva (compare figs. 29 and 30) . 

 The antennae are located on the upper side of the head, 4-jointed, 

 1st joint, 3.25 mm.; 2nd, .24 mm.; 3rd, .64 mm.; 4th, .64 mm. 

 (Figure 31). An antennal sclerite is present and well differentiated. 

 Each eye consists of six ocelli, situated behind and below the an- 

 tennae in two parallel rows ot three each. 



Fig. 30. — H. triangularis, mature larva. 



