324 M. Leuckart on the Reproduction of Bark-lice, 



with a woolly down, but this is very much shorter. Like 

 their parents, they are subject to a repeated change of skin 

 as the size of their bodies increases, but they do not by this 

 means perceptibly alter in their appearance. Towards the end 

 of July these larvse become converted into pupae ; they then pre- 

 sent wing-cases, and are all attached, almost immoveably, with 

 the legs retracted, by means of the rostrum, to the wall of the 

 cell. In about a fortnight the metamorphosis is complete; 

 the cells of the galls open, by the separation of the leaves, 

 which gradually dry ; and from the gaping fissures the crowd 

 of pupae, which have again become capable of motion, escape, 

 usually in the sunshine. These ascend the leaves in the vicinity, 

 cling firmly with their legs, and then, by another change of 

 skin, become converted in a few minutes into winged Aphis-like 

 creatures, which remain sitting close together for a time on the 

 leaves, and then disperse in all directions. 



In the course of a few days, single individuals of these Aphides 

 are found dead, with their wings spread out in a rooflike form, 

 here and there upon the leaves, and beneath them a small aggre- 

 gation of pedunculated eggs, partly enveloped in the woolly 

 hairs, adhering to the abdomen of the mother. The young, 

 which escape from the eggs in the course of a few weeks, dis- 

 perse themselves, and seek the developed buds in the vicinity, 

 usually singly, seldom two or more together ; upon these, as 

 above stated, they hibernate, and in the next year, with a more 

 abundant nourishment, produce a new progeny. 



Our present knowledge of the Fir-lice is confined to the pre- 

 ceding observations. No one has yet seen the copulation of these 

 animals, nor has any one yet proved with certainty the exist- 

 ence of a male. It is a mere assumption that a copulation pre- 

 cedes the oviposition of the winged animals ; and it is nothing- 

 more than an assumption when Ratzejburg [op. cit. p. 201) 

 regards the smaller individuals of this winged generation as 

 males, and considers the elongated form of their abdomen, and 

 the presence of an obtuse penis-like organ (Ruthe) protrusible 

 by pressure with the compressorium, as characteristic attributes 

 of their sex. The same questions still remain to be answered 

 with regard to the reproduction of the Fir-lice, that De Geer 

 proposes at the end of his account of the natural history of these 

 animals. 



I am happy that my investigations enable me to give some 

 more definite information upon the conditions in question. This, 

 however, is not in favour of an opinion which not long since 

 held the place of an irrefragable law, and which also influenced 

 the earlier observers in their suppositions. 



/ have convinced myself that the reproduction of our Fir-lice 



