2\G Mr. G. R. Waterhouse's Monograph on 



Several of the species of Diphucephala very closely resemble each 

 other, and might easily be confounded unless minutely examined ; 

 and as in writing this monograph it has been essential that I should 

 do so, it occurred to me that much time might be saved to those 

 who may use the following descriptions in investigating the species, 

 were I to make a few preliminary observations upon the characters, 

 which have been chiefly chosen by me for their separation. 



With respect to the form, the deeply emarginated clypeus has 

 been mentioned as a generic character ; there is however consider- 

 able variation as to the extent of the emargination, and the form of 

 the lateral processes, as I have termed the projecting parts of the 

 clypeus, caused by the deep emargination. 



In D. sericea the emargination in the males is moderate. In D. 

 Childremi, Hopei, and affinis the emargination is very deep, and the 

 projecting processes either have the inner edges parallel with each 

 other, or else their apices are somewhat approximating. In Z). Ed- 

 wardsii the emargination is also deep, but the lateral processes are 

 slightly diverging. D. splendens and pulchella have the emargina- 

 tion of the cljrpeus moderate, the projecting processes not very wide 

 apart, but diverging at the apex. In the remaining species the 

 clypeus is not deeply emarginated, and the projecting processes (in 

 all excepting /7art;M/a) are wide apart and diverge at the apex. 



The length of the thorax is generally about equal to the width 

 (which is slightly narrower than the elytra); it always has the ante- 

 rior part truncated, the posterior margin dilated in the region of the 

 scutellum, and the posterior angles more or less acute. The lateral 

 margins are always straight, and parallel with each other, posteriorly ; 

 dilated in the middle, and from thence contracted gradually to 

 about the same width as the head. In D. pulchella, aurulenta, pili- 

 striata, and Spencii the dilated part of the lateral margin is produced 

 into a tooth-like process ; in the remaining species it is rounded or 

 somewhat angular. 



since in our present subjects, as well as in bees, there is a similar difference in the 

 structure of the claws of the two sexes. In the males the divisions of the bifid claws 

 are of equal length or nearly so ; whilst in the females the inner portion of each is 

 considerably shorter than the outer; the claws are also less deeply cleft in the fe- 

 males. In the sexes of D. sericea these characters are very evident. In the male 

 of/). splende7is the inner division of the claw is not quite so long as the outer, (in 

 which respect this species differs from the same sex of the foregoing, as in that they 

 are quite equal,) still between the male and female there is an evident difference in 

 the proportionate length, as may be seen by comparing the drawings. 



I should not have dwelt upon these points, but it appeared that by thus observing 

 the same peculiarities in different orders, which nevertheless resemble each other in 

 some of their habits, we may gain a clue to the discovery of the uses of such structure. 



