and Life History of Psychoda sexpunctata. 305 



or to breathe the air dissolved in the water, and dies in a 

 few days. 



The Head and its Appendages in the Fly. 



The head is almost vertical. (Figs. 11 and 12.) Seen 

 from above it is transversely oval ; the front surface is pear- 

 shaped, narrowing downwards to the labrum. The com- 



Fig. 11 ( x 80). 

 Head of fly. 



pound eyes are horse-shoe shaped, and nearly meet above. 

 They contain comparatively few ommatidia, not more than 

 live or six rows in the widest part, and possibly about 

 eighty in all. 



Immediately within the lower ends of the horse-shoe- 

 shaped compound eyes can be seen in the openings of a 

 pair of chitinous tunnels which perforate the head. They 

 run through it obliquely, and their openings on the back of 



