362 Proceedings of the Royal Society of Edinburgh. [Sess 
fmidatrix derived from a gallicola non-migrans. From these data and 
from morphological evidence he has deduced that the parthenogenetic 
species of Cholodkovsky have no existence, and he has united the two 
branches into one species, Chermes abietis, L. ; similarly for Gnaphalodes 
strobilobius, Kalt. Further, he (3) stated that from the eggs laid by the 
colonici two types of larvae hatched, the sistens and progrediens types 
(hiemalis and aestivalis of Borner). 
The following are the cycles of the above species according to Borner 
(4-10) : — 
Diagram 5. — Graphical representation of the life-history of Chermes abietis (L. ), Borner, according 
to Borner. 
Diagram 6. — Graphical representation of the life-liistory of Cnaphalodes strobilobius (Kalt.), 
Borner, according to Borner. 
In reply Cholodkovsky maintained the existence of the parthenogenetic 
species, and stated that he had not observed two different kinds of larvae 
hatching from eggs laid by colonici. In 1909, while on holiday in Switzer- 
land, he (27) observed gallicolae of abietis type on spruce, which in them- 
selves and their progeny differed from those of Chermes abietis , Kalt., 
observed by him in Estland, Russia. Cholodkovsky then concluded 
that there were three species of this type in Europe: a Western species, 
which he named Chermes occidentalism probably possessing both gallicolae 
migrantes and non-migrantes, with two species, Chermes abietis , Kalt., and 
Chermes viridis, Ratz., in North and East Europe, the former with non- 
migrantes and the latter with migrantes gallicolae. 
Ntisslin (45) has contributed to the knowledge of the genus Dreyfusia, 
and has published valuable and suggestive criticisms on the theories as to 
the origin of migration (46). 
Marchal (43) in France has worked on the genera Pineus and Dreyfusia. 
He has shown that the species of these genera have a complex life-history 
on the intermediate hosts, pine and silver fir respectively. 
