10 Mr. S. S. Saunders on 



By the discriininating characters derived from the 

 shape and number of these several joints (which, in con- 

 junction with certain differences in those of the tarsi, 

 have served as a basis for generic distinctions, and are 

 also found to maintain a constant restriction to certain 

 exclusive associations of birth and origin), it may as readily 

 be determined to which section of the Stylopidce any 

 nurturing race or foster-parents may have afforded suste- 

 nance, as vice versa to which tribe of the latter any of 

 the aforesaid should be affiliated, in so far as such con- 

 necting links have been duly ascertained in other cases. 



Hence it would seem to follow, as a necessary corollary, 

 that all combinations of such genera into natural groups 

 or subfamilies, should be made in accordance with their 

 respective alliances ; whereby these associations may be 

 consistently defined and maintained. lu fact, there is 

 no other possible criterion for properly assorting the 

 females, than by classifying the nurturing species them- 

 selves in conjunction therewith. 



The genus Xenos, however, as at present constituted 

 (by reason of a mere coincidence in the number of joints 

 in the antennae and tarsi) , is subject to the controlling 

 destinies of different families and tribes, so widely 

 separated from each other in the most vital elements of 

 their existence, as to render any artificial union between 

 their respective dependents, founded upon this limited 

 basis, utterly irreconcilable with such obvious incompati- 

 bilities of origin and descent. 



Thus the true Xenides consorting with the social Vcs- 

 pidcB, must be reared from their primary hexapod condi- 

 tion in from thirty to forty days : such being the term 

 within which the larvae of the Social Wasps attain the 

 imago state; the females of the latter hyhernating ^x\th 

 those of the former, which produce their larval brood the 

 ensuivg year. 



In marked contrast with these hybernating Xenides, 

 which, from the peculiar exigencies thus imposed, are 

 slow to produce their larval brood from females of the 

 preceding year, hut rajnd^ in their ultimate metamorphoses ; 

 others have been comprised in the same group, which 

 are nurtured by the larvee of solitary wasps and fossorial 

 Hymenoptera, these latter tribes coinciding more or less' 

 in their habits and economy, and requiring about eight 

 or nine months (from one year to the next) to attain 



