ms.] 223 



SOME NEW CONSIDERATIONS ABOUT PLANT-LICE. 

 BY J. LICHTENSTEIN. 



In reply to my " Enquiry about plant-lice " (p. 175, ante) I have 

 had the pleasure of receiving some very interesting communications 

 fz'om various quarters ; and, after watching ■s\ith the greatest care the 

 cj'^cle of life in about half-a-dozen plant-lice, from the fecundated egg 

 up to the adult female, I arrive at the following conclusions : — 



Ordinarily, insects are dioecious, that is, each sex is already se- 

 parate in the egg, and two eggs are necessary to produce a male and 

 a female. But the Aphides are monoecious, that is, a single egg is 

 sufficient to produce, not only one male and one female, but a great 

 quantity of males and females, thus evidently the two sexes are in- 

 cluded in the fecundated egg. I do not know that this is mentioned 

 anywhere, but I have seen very few works on embryology, so, perhaps, 

 it is already known and recorded, and also the difference between a 

 dioecious and a monoecious egg has been discovered. 



At all events, in the Somoptera-dioecia {Cicada, Psylla, Aleurodes) 

 a very good character thus exists to distinguish them from the 

 Homoptera-moncecia {Apliides) . (I make a reservation about Coccido'.) 

 But as the single mother-louse (which, of course, possesses no separate 

 sexuality, any more than the egg itself) gives birth to a second and 

 third stage of generation equally agamous, and it is only in the fourth 

 stage that male and female appear in sejjarate forms, the matter 

 becomes far too elaborate to be treated in a single note like this. So 

 I now content myself with enquiring only of your readers if they are 

 aware whether the fact of the monoecious nature of the Aphides has 

 been mentioned or not. 



Relative to my enquiry about the sexuated forms of plant-lice, 

 I have received the following highly interesting communications: — ■ 



Dr. Franz Low, of Vienna, knows Pemphigus Boyeri (subter- 

 ranean) and Pemphigus spirothecce (gall-louse) as giving birth in the 

 W'ingcd state (my pupiferous form) to sexuated unwinged lice without 

 rostrum, but he docs not believe that the last mentioned species has an 

 underground stage in the cycle of its life. 



Prof. Dei'bes, of Marseilles, says that Pemphigus coniicularitis has 

 been the object of his studies, and he will shortly publish the result. 

 The pupiferous form, which he calls "aile du printouq)s," appears in 

 the spring, depor^its its pupa> on Pistacia terehinthus, and Ihe remainder 



