MISS EMBLETON OX Ci;H.\T,V.l'/rrs LATANI.E. 101 



BpinoHUH, Shimer, Aphids that make gallw on the leaves of the 

 witch -liazel {Tlamamelis virr/iniana) m North America. The 

 individijjjlH in the gall pa-sH througli a rnetamorphosis, appearing 

 in a different form after each ecdywiH. The individuals of this 

 generation are not winged, hut remain on the host plant, and 

 produce a second generation within the wallr^ of the gall. The 

 individuals of* this generation alno undergo their development 

 and metamorphoais in,side the gall, but they differ essentially from 

 those of the first generation inasmuch as they develop wings and 

 all nltimat(;ly leave the shelter of tha gtill. 



From the witch-hazel these winged forms migrate to the birch 

 (Betala nUjra), where they immediately place their young, so 

 that the species n^m lives not in galls but exposed on birch- 

 leaves. Thiii third generation undergoes a complex meta- 

 morphosis, the successive instars being very different from one 

 another ; the last instar so closely resembles many Aleurodidtj;^ 

 that Pergande has called it the " aleurodifurm " stage. In 

 calling it " aleurodiform " it may be as well to remark here 

 that it is the young Aleiirodes which the Aphis resembles, and 

 not the adult form. 



While living on the birch, two other aleurodiform generations 

 (i. e. the fourth and filth) are passed through, but they differ 

 only very slightly from the third. 



The sixth generation is remarkably different. In this genera- 

 tion the insect is winged and leaves the birch to return to the 

 hazel. It may t-afely be taken for granted that hitherto all 

 the individuals produced have been females, but a seventh 

 generation arises in which both sexes occur. Eggs are laid 

 before the leaves appear in the spring, the young hatching from 

 these eggs start the galls, and the life-cycle is begun once 

 more. 



From this work by Pergande it will be seen that CeratapJdn 

 latanicB found on orchids corresponds to the aleurodiform stage 

 of a migratory Aphis, such as he has described in the case of 

 Jlormapkis hamamelidifs and its ally. In these insects, however, 

 the stage is transit^^ry, and is usually succeeded by a winged 

 form ; but in the case of Gerata'phis in Britain, it seems that 

 no further stage is reached. So far as the observations in 

 Caaibridge go, they lead us to believe that this aleurodiform 

 stage ib the permanent condition of the insect ; in spite of the 



