M. Leuckart on the Rqwoduction of Bark-lice. 415 



The greatest number of egg-tubes occurs in the wingless fe- 

 males of Chermes Abietis, which is also by far the most prolific 

 of all Bark-lice. In this species T have counted 20-24 egg- 

 tubes on each side — a number which almost reminds one of the 

 structure of the ovary in the Coccina^, to which our plump 

 animals (like the rest of the wingless Bark-lice) also bear an 

 external resemblance. In the winged individuals the number 

 of egg-tubes varies between far greater extremes : I have met 

 with individuals with 24 and 30 egg-tubes in all, and with 

 others which had only 10. The latter specimens were at the 

 same time much smaller than the others ; they are Ratzeburg's 

 so-called males. In the number of egg- tubes, Chermes Abietisis 

 approached most closely by the genus Phylloxera^ the wingless 

 females of which usually exhibit five egg-tubes on each side. 

 Chermes Picece J in the wingless state, possesses three or four egg- 

 tubes on each side (sometimes also nine in all). The number is 

 lowest in C.Laricis, the wingless individuals of which very con- 

 stantly possess six egg-tubes, whilst the winged examples (fig. 1) 

 usually present only four (but sometimes five) in all. 



The oviducts to which the egg-tubes are attached are, as in 

 the Aphides, of but inconsiderable length, and have a distinct 

 muscular layer, with fibres which principally run in a transverse 

 direction and are repeatedly branched. A very similar but 

 still more strongly developed muscularity is also possessed by 

 the single oviduct. 



In the oviparous Aphides and the Coccina there are, as is 

 well known, two different kinds of accessory structures on this 

 oviduct, — a pair of sac-like or tubular organs with fatty con- 

 tents, which we shall indicate as a lubricating gland {Schmier- 

 driise), and at a greater or less distance above these, a roundish 

 or pyriform pouch, the receptaculum seminis. The case is very 

 diff'erent in our Bark-lice (fig. 1). On a superficial examination 

 we find only two accessory organs, which are attached at about 

 the limit of the posterior third of the oviduct, and show themselves 

 to be the lubricating gland, notwithstanding several peculiari- 

 ties, both by their structure and the nature of their contents. 

 Above this gland we may seek in vain for another appendage ; 

 but, on the other hand, far below, immediately over the obtuse 



individuals amongst the Aphides ; at least, 1 have hitherto met with the 

 unilocular germ-tubes first described by me only in winged individuals of 

 these animals. Nevertheless, it can by no means be said that all winged 

 Aphis-nurses possess unilocular germ-tubes. I also know species the 

 wmged nurses of which are provided with plurilocular and multilocular 

 germ-tubes. 



* In the true Aphides I have never met with more than four egg-tubes 

 on each side. 



