1006 INSECTS AND AKACHNLDA 



(Miica vomitoria). 1 In order to preserve these eggs they should 

 be mounted in fluid in a cell, since they will otherwise dry up, and 

 may lose their shape. They are very good objects for securing some 

 of the best binocular effects. 



The remarkable mode of reproduction that exists among the 

 Aphides must not pass unnoticed here, from its curious connection 

 with the non-sexual reproduction of Entomostraca and Roil f era, as 

 also of Hydra and Zoophytes generally, all of which fall specially, 

 most of them exclusively, under the observation of the microscopist. 

 The Aphides, which may be seen in the spring and early summer, 

 and which are commonly, but not always, wingless, are all of one 

 sex, and give birth to a brood of similar Aphides, which come into 

 the world alive, and before long go through a like process of multi- 

 plication. As many as from seven to ten successive broods may thus 

 be produced in the course of a single season ; so that from a single 

 Aphis it has been calculated that no fewer than ten thousand million 

 millions may be evolved within that period. In the latter part of 

 the year, however, some of these viviparous Aphides attain their full 

 development into males and females ; and these perform the true 

 generative process, whose products are eggs, which, when hatched in 

 the succeeding spring, give origin to a new viviparous brood that 

 repeat the curious life-history of their predecessors. It appears from 

 the observations of Huxley 2 that the broods of viviparous Aphides 

 originate in ova which are not to be distinguished from those 

 deposited by the perfect winged female. Nevertheless, this non- 

 sexual or agamic reproduction must be considered analogous rather 

 to the ' gemmation ' of other animals and plants than to their sexual 

 ' generation ; ' for it is favoured, like the gemmation of Hydra, by 

 warmth and copious sustenance, so that by appropriate treatment the 

 viviparous reproduction may be caused to continue (as it would 

 seem) indefinitely, without any recurrence to the sexual process. 

 Further, it seems now certain that this mode of reproduction is not 

 at all peculiar to the Aphides, but that many other insects ordinarily 

 multiply by ' agamic ' propagation, the production of males and the 

 performance of the true generative act being only an occasional 

 phenomenon ; and the researches of Professor Siebold have led him to 

 conclude that even in the ordinary economy of the hive-bee the same 

 double mode of reproduction occurs. The queen, who is the only 

 perfect female in the hive, after impregnation by one of the drones 

 (or males) deposits eggs in the ' royal ' cells, which are in due time 

 developed into young queens ; others in the drone cells, which become 

 drones ; and others in the ordinary cells, which become workers or 

 neuters. It has long been known that these last are really un- 

 developed females, which, under certain conditions, might become 

 queens ; and it has been observed by bee-keepers that worker-bees, 

 in common with virgin or unimpregnated queens, occasionally lay 



1 Compare R. Leuckart in Archiv f. Anat. 1853, p. 90, ' Ueber die Micropyle und 

 den feinern Bau der Schalenhaut bei den Insecteneiern,' and A. Brandt, Ueber das 

 Ei und seine Bildungstatte, Leipzig, 1878. 



2 ' On the Agamic Reproduction and Morphology of Aphis ' in Trans. Linn. 

 Soc. xxii. p. 193. For observations on American Aphides see various papers by 

 Mr. C. M. Weed in Pysclie and other American journals. 



