106 Proceedings of the Royal Society of Edinburgh. [Sess. 
were males and two were females. From the first these larvae, which 
were reared on the same leaf, were distinct in colour — the males being 
bright green and the females pale yellow. Subsequently mating took 
place and eggs were laid. 
The period of development of the oviparous females varied between 
sixteen and forty-five days. That of the males was twenty to twenty-five 
days. The total length of life ranged from twenty-nine to sixty days for 
females, and from thirty to thirty -five days for males. Oviposition did 
not take place until two or three days after copulation. Dissections of 
eight females yielded on an average five large eggs each, with others at 
various stages in the ovary. The eggs were occasionally deposited on 
the leaves, but for the most part the aphides crawled to the stem or into 
the axils of the buds for the purpose. One male may fertilise two, or 
probably more, females. 
Thus it is clear that migration to the second host plant is not obligatory 
in this species, since the sexual' forms can be produced after an unbroken 
cycle on currant. Mordwilko (20) writing of A. sambuci, Linn., says: 
“ If this species is proved to migrate from elder, we should have the 
interesting problem of the sexuparm produced on the first host plant ; and 
this does not occur in any other of the migratory Aphidince A As the 
foregoing observations show, this is the case with M. ribis, a form unique 
in this respect in the sub-family. Moreover, the males and oviparous 
females may be produced on the second host plant also, a condition which, 
as far as I know, does not obtain with any other of the Aphidince. 
Winged males appeared at the beginning of October upon Galeopsis. 
They were the progeny of two winged females of the A. I, 17 generation 
{ribis stock transferred to Galeopsis ) and were indistinguishable from the 
males born on currant. Buckton (2, p. 172) says that the nymph of the 
male of Phorodon galeopsidis is very small and has a broad head, but these 
nymphs were identical with those of the winged viviparous females. The 
males from Labiatae mated when placed with oviparous females from 
currant, and eggs were laid after such unions, but the females were unable 
to live or oviposit on Labiatse. 
Until the end of October, no oviparous females appeared among the 
Galeopsis stock. The researches of Mordwilko and others show that in 
other species of migratory Aphidince the male alone is born on the second 
host, and that the eggs are never laid there. The observations of Van der 
Goot ( Beitrdge zur Kenntnis des Hollandischen Blattlause) seemed to 
confirm this for M. ribis. He records that migrants of P. galeopsidis 
appeared on currant in the autumn, and that oviposition took place on 
