Miscellaneous. 433 



Metamorphoses of the Aphis of the Woody Galls of the Black Poplar 

 (Pemphigus bursarius, Linn.). By H. J. Lichtenstein. 



By indicating as synonymous with his Aphis bursaria the Aphides 

 of which the galls are figured under the nos. 7-11 in pi. xxvi. of 

 Reaumur's third volume, Linne has set his successors a problem to 

 solve ; for in this case the choice is embarrassing. Fig. 8 of the 

 great French observer in fact presents, under the letters h, g, u, 

 very different galls united on the same branch ; and the entomolo- 

 gists who have copied Linne have taken sometimes one and some- 

 times the other species for Aphis bursaria. 



Without wishing here to perform 'a work of criticism, I shall 

 confine myself to saying that I regard as Pemphigus bursarius the 

 insect of the gall figured by Reaumur under the letter h. It is the 

 only gall that is fixed upon the bark ; it is the only one that is of 

 a hard woody consistency ; further, it does not fall with the leaves ; 

 it is persistent, and may be very readily seen upon the poplars 

 during the whole winter. 



Up to the present time we have only known of the insect which 

 forms this gall, the foundress-mother, and the emigrant winged 

 progeny which quit the galls in June and July. No one has yet 

 been able to discover where this emigrant form goes, nor have I 

 been able to fill up this gap ; but having placed in a tube these 

 winged emigrant insects, I soon saw them deposit living young, all 

 alike, and presenting a well-developed rostrum, a certain indication 

 that they are destined to take food ; only I have not yet been able 

 to find what suited them, and they have all died in my bottles. 



Now, in freedom, in the month of August, when the last emi- 

 grants had quitted the galls, I have seen arriving upon the poplars 

 winged insects which, quite in opposition to the emigrants, seemed 

 to endeavour to enter instead of issuing forth, and this, not only 

 into the already dry galls, but into all the fissures of the bark. 



The external appearance of these Aphides is almost the same as 

 that of the emigrant form ; I can find no difference between them 

 except in the number and form of the crenulations of the third joint 

 of the antennae, which run all round the antennae in the emigrant, 

 and only pass half round in the new comers. But their pro- 

 duct is quite different. Placed in tubes the new arrivals deposit 

 what I call pupce in the Phylloxera?, and pupae of two sizes, which 

 very quickly free themselves from their envelope, and give origin to 

 small sexual Aphides, male and female, destitute of the rostrum, 

 and furnished with generative organs. Copulation takes place; and 

 soon afterwards the female deposits, between the wrinkles or cracks 

 of the old drying gall, a small yellow egg, surrounded by a white 

 cottony down or secretion. 



Is it not marveDous to see instinct thus carry back the Pupiferae 

 to the dwelling formed by their great grandmother, to bring back 

 to it the young couples which are to furnish the single egg, the 

 germ of the future colony ? 



Of this egg I have preserved numerous examples in my cabinet 



