390 Atiscellaneous. 



On the Sexual Generation of Chermes abietis, Linn. 

 By Dr. F. Blochmann. 



I was led by the preparation of my lecture " Ueber ausgewahlte 

 Kapitel aus der Fortpflauzungs- und EDtwicklungsgeschichte der 

 Thiere " to attend in more detail to the cyclical development of the 

 Aphides, and in this way I became aware of many still existing 

 gaps in our knowledge. One such hiatus is to be found in the 

 history of the reproduction of the genus Chermes, seeing that, 

 notwithstanding the eiforts of various distinguished observers, it was 

 still undecided whether a sexual generation does or does not occur 

 in its cycle of development. As the galls of Chermes are very 

 abundant at many places here in Heidelberg, and especially on the 

 so-called " Himmelsleiter," I took occasion during my walks to 

 observe their development, in order to detect the sexual animals, 

 the existence of which I fully expected to find from the great 

 similarity of the course of development in Chermes and Phylloxera. 

 In this I soon succeeded, and I would not omit giving a short 

 communication here, especially because at the moment I am not in 

 a position to furnish a detailed description with figures. 



For the most detailed observations upon the life-history of the 

 Bark-lice we are indebted chiefly to Eatzeburg* and Leuckartf. 

 What is known from them is as follows:— In the autumn we find 

 at the bases of buds of the fir small wingless animals covered with 

 grey wool, which have buried their long proboscis deeply in the 

 tissues, and in this position live through the winter. In the spring 

 they grow considerably, with several changes of skin, the sexual 

 organs especially becoming developed. The investigation of the 

 latter shows that the animals are all xmfertilized females. They 

 now begin to lay a great number (up to about ^00) of peduncu- 

 lated eggs, which remain lying under the mother, enveloped in dense 

 white wool. These soon become developed into female larvae, which 

 crawl between the leaves of the expanding bud. These are already 

 deformed at the base of the bud by the sucking of the mother, and 

 become still more so now by the united efforts of the brood, so that 

 the well-known pineapple-like galls are produced. I may state 

 here that of the two species, which are usually distinguished by.the 

 formation of their galls, the one which makes the smaller galls 

 {Chermes coccineus, Eatz. = C. strobilobius, Kalt.) has served for my 

 investigations. 



In the galls the young animals increase in size, with several 

 changes of skin, and develop wing-sheaths. At the beginning or 

 middle of June the different chambers of the gall open, the nymphs 

 crawl out upon the leaves of the nearest twigs, and then change 

 their skin for the last time. After this moult they appear as winged 

 insects, which, in fine weather quit the twig and settle themselves 



* Die Forstinsekten, Bd. iii. pp. 195-205 (1844). 



t " Die Fortpflanzung der Rindenlause," in Arch, fiir Naturg. 1859, 

 pp. 208-231. 



