terminal segment in some male Ilemlptera. 419 



were a protecting shield for any other purpose than 

 shelter against the pressure of the cauda, it would be 

 specially required in this species : thus its absence where 

 the Cauda does not come into relation with the oedeagus 

 suggests very strongly that its function is protection 

 against the pressure of the cauda. 



The cedeagus. — This of all the accessory male parts 

 is, of course, the most important, being the part most 

 directly engaged in the process of fertilisation. But it 

 is of all the parts the most variable ; it is, indeed, so 

 extremely different that I cannot with certainty homologise 

 the parts in some of the forms. As instances of extremely 

 different forms of oedeagus I may mention Pa'cilochroma 

 lata, Eusthenes j^ratti, Stilida indecora, Edcssa riifo- ■ 

 marginata, and Piezosternum suhdatmn. Notwithstanding 

 the difficulties of homologising the parts of the oedeagus 

 (which is complicated by its variable relations with the 

 theca), I would suggest that it may ultimately prove to 

 consist in all these insects of three parts, viz., two lateral 

 lobes similar to one another, and a single median ligula 

 or style. But to assert this positively examinations 

 must be made of a large number of species in a fresh 

 condition. 



The oedeagus in the Pentatomidce is not capable of 

 being thrust out of the body as it is in Coleoptera ; it 

 consists of two arms, the basal one of which is fastened 

 to the floor of the terminal segment; to this basal 

 portion the part of the oedeagus usually visible is fastened 

 by a transverse joint. In repose this outer part of the 

 cedeagus is bent up and so concealed, while for the pur- 

 pose of copulation it is defiexed ; if it exercise any 

 movement during copulation — which appears to me very 

 doubtful — it must be that of elevation or depression of 

 the part external to the transverse joint. 



The true intromittent organ, as seen in E. pratti, is a 

 very elongate, transparent tube, similar to a glistening 

 white thread ; its great length is very remarkable. 



IV. General remarks. 



Although very little can be said as to the special 

 functions of the parts I have described, and although it 

 is as yet very difficult to form any idea likely to be of 

 importance as to the reason of their existence, yet there 



