')0 B C. KXTOMOLOGICAL SOCIKTY. 



the islands and vn the mainland, this coupled with the fact that an unde- 

 termined species has been collected for mice, strengthens the supposi- 

 tion. 



An interesting; lial^it of Cuterelirine larxae mentiimed Ijy Townsend 

 is their custom of emerging after their host animal has been killed. Thi.s 

 apparently takes place only when they are sufficiently mature to pupate. 

 Confirmation of this habit has been obtained from observers in P.ritish 

 Columbia. The occurrence has not been obser\ed in Hypoderma, and 

 seems peculiar to the parasites under discussion. 



Through the kindness of Dr. C. Gordon Hewitt 1 have iii)tained 

 Townsend's original description of C. fontinella, and find that he gives 

 no description of the ovipositor. The most striking thing about the 

 ovipositor is its shortness, as compared with those of the other Oestridae ; 

 and this fact makes one wonder how oviposition is accomplished on, for 

 instance, a small active rodent? One experiment was made with the fly 

 mentioned in the first part of this paper. Immediately after it was cap- 

 tured it was placed in a jar with a white mouse. The mouse became 

 terrified, and whenever the fly buzzed against it, the mouse turned 

 viciously and bit at it. The experiment was, of course, a failure, as both 

 mouse and fly wanted to escajje. 



Description of the Ovipositor. 



The ovipositor is very short and set in a horse-shoe space, the open- 

 ing being toward the \'entral part of the insect. (Plate 3, Fig. 7). The 

 horse-shoe ring is surrounded by what Townsend describes as the fourth 

 and last segment of the abdomen. He is certainly wrong in this, as 

 there are two distinct segments following the fourth, forming part of 

 the ovipositor, and, in addition to these, the sternite and tergite plates 

 represent suppressed segments. So that there are at least six visible 

 segments in the abdomen. All the segments, including the ovipositor, 

 are densely covered with hairs, a fringe of hair on the margin of the 

 fourth segment partly conceals the ovipositor. 



The ovipositor ends in two blunt processes, which correspond to 

 the latero-sternal sclerites, and another, the tergal sclerite, described by 

 Carpenter for Hypoderma. (Plate 3, Fig. 6). N'entrally in front of the 

 tergal sclerite, there is a chitinous plate which fits between the latero- 

 sternal sclerites. 



In front of the chitinous plate is a paired membranous organ with 

 two points, which are designated in the figures as paired membranous 

 processes. (Plate 3, Figs. 5 and 6). 



I am indebted to Mr. Hugh Scott, Curator in Entomology at Cam- 

 bridge, and Mr. E. E. Austen of the British Museum for the determin- 

 ation of C. fontinella; to Mr. G. H. Unwin for collecting literature, and 

 to Dr. F. Torrance, Veterinary Director-General, for permission to pub- 

 lish this article. 



