Two new Streps ipterous Insects. 49 



tible, doubtless, of some subtle appreciations of external in- 

 fluences, although deprived of independent action and visual 

 discrimination. The earliest specimens producing these hex- 

 apods, taken at large with the Hylcei, were found towards the 

 beginning of the fourth week in June; which, assuming the final 

 metamorphosis of the bees to have been at least synchronous 

 with the most precocious of those produced in the house, would 

 indicate about three weeks as the usual term of gestation in these 

 parasites on Hylceus; nearly agreeing with Mr. Newport's compu- 

 tation in the case of his Stylops aterrlma, namely, about eighteen 

 days. 



It has, however, been announced by Dr. Siebold, as if generally 

 applicable throughout this class of parasites, that the hatching of 

 the eggs in the Strepsipterous females proceeds very slowly (geht 

 sehr langsam vor sich), and that many of the latter hybernate 

 with the insects upon which they subsist (29th result); which ob- 

 servations however can only be understood as applicable to the 

 females of Xcnos; and indeed, under the peculiar embryogenous 

 and metamorphotic conditions affecting the continuation of the 

 species, it is manifest that these parasites could not perpetuate 

 their existence in company with the social Vespidce, unless the 

 epoch of parturition were thus protracted until the following 

 year, so as to enable them to transfer their hexapod progeny to 

 the succeeding colony of wasps. In the case of Stylops, how- 

 ever, the converse necessity exists for the rapid development of 

 the ova, the Andrence enjoying but a limited term of existence at 

 large, and it being therefore essential that, within the brief period 

 of a few weeks, the female parasite should fulfil the part assigned 

 her, and the young hexapods be ready to occupy their appointed 

 stations in the larva cells of the bee, soon about to be closed. A 

 corresponding urgency is imposed upon these parasites on Hy- 

 lceus; although the larva state of the latter continuing throughout 

 the winter and spring, involves the necessity of a suitable con- 

 formity of habit in the parasite, under those altered conditions 

 wherein nature, in the plenitude of her resources, delights to 

 exhibit her ever-varying appliances. 



The pupae of the males, as Dr. Siebold proceeds to explain, 

 always first appearing at the beginning of summer, (immer erst 

 im anfang des sommers,) but never surviving the winter : it 

 follows that the hexapod larvae to which he alludes, produced 

 before the aforesaid pupae of the males, must, by a speedy tran- 

 sition, assume the pupa state at the time when these latter are first 

 observed ; which well accords with the habits and equally rapid 



VOL. I. N.S. PART II. OCT. 1850. E 



