Nov., 1908.] The Broken Hemelytra in certain Halobatinae. 39 r 



Bergr., Rh. tenuipes Mein. and Trepohates pictus H. S. the 

 hemelytra extend much beyond the end of the abdomen, being 

 about twice as long as the latter. In all three the male is 

 smaller than the female and has a somewhat shorter abdomen. 

 In consequence the male has to sit quite far back on the female 

 in copulation, in order to approach her genitaha. Now, long 

 wings in the female would be decidedly in the way of the male, 

 as can be readily appreciated, provided they did not actually 

 prevent the generative act altogether. In consequence, the 

 female finds it imperative to shorten her wings in order to give 

 access to the male, which she does by breaking them off at the 

 line of weakness, thereby leaving the greater part of the abdomen 

 exposed. But vvhile this would seem to be an explanation of the 

 act in the female, it scarcely covers the case of the male, since his 

 genitalia are in no way covered or directly prevented from coming 

 into contact with those of the female by his long hemelytra. In 

 the length of the tegmina, however, lies the clew. Both Tre- 

 pohates and Rhemnatohates rest very close to the surface of the 

 water, so much so that the body of the latter seen from above 

 seems to touch the surface, although when seen from the side it 

 can at once be noted that such is not the case. Now, as pointed 

 out above, the males in both these genera have to sit far back 

 on the females, and in that position the tip end of the hemelytra 

 would produce an indentation in the surface film or be sHghtly 

 submerged. The smallness of the bug would tend to make it 

 appear that the former would be the case. This resistance, of 

 course, would operate in two ways. It would be a great assist- 

 ance to the unwilling and struggling female in getting rid of the 

 amorous yet unwelcome male; and it would be decidedly in his 

 way by preventing the approach of his genitalia to hers. Hence 

 the male, for similar reasons to the female finds it necessary to 

 rid himself of members which, while they may at some period 

 subserve a useful purpose, are decided obstacles to the real end 

 of insect life. 



The second solution offered in explanation of this self-mutila- 

 tion is grounded on the following observations. 



The first truncate winged Rheumatobates I captured was in a 

 deep currentless pool in a stream, by no means a normal breeding 

 place. All the others, as well as the Trepohates were found, as 

 previoush' noted, in a small pond which at a time when St. 

 Mary's Lake had its full quota of both forms in several instars, 

 had not a single individual of either on its placid surface. But 

 later, when the Lake w^as populous with adults, some fully 

 winged, the pond had on it all these truncate winged individuals 

 as well as a few nymphs and some wingless adtilts. It may well 

 be, therefore, that the object of the wings is to facilitate migra- 

 tion, either to provide against in-breeding, or to allow their 



