Insects, etc.., Injurious to the Damson. 



251 



partly from the produce of the migrants from the hops and rarely 

 from the hops themselves the winged males appearing some ten 

 days later than the winged female migrants. These males fertilise 

 the oviparous wingless females, and may be found in numbers 

 in copula on the prunes. In about two days after copulation the 

 females deposit one or more greenish eggs, which soon become black. 

 They commence ovipositing in October in small numbers ; great 

 numbers of eggs have been observed by the 22nd, oviposition 

 ceasing on the 8th of November. Here the eggs remain all the 

 winter, starting fresh in the spring, as previously narrated. 



Pliorodon humuli can, however, carry on its existence in another 

 way. On two occasions aphides have been found on the hop-shoots 

 early in the year (April). During the winters of '96, '98, and '99, I 

 frequently searched for humuli in 

 the hop-hills and on broken bine, 

 both as eggs and aphides. In 1898, 

 in February, I found two wingless 

 viviparous females in the hills. It 

 appears, therefore, that continuity 

 may be carried on during the winter 

 in that way as well as in the egg 

 stage on prunes. Several observers 

 have told me that they notice lice 

 on the hops early in the year, and 

 probably these have wintered in the 

 hills, and commence to give rise to 

 young as soon as the weather be- 

 comes favourable. In experiments 

 conducted at Stoke Edith in 1884, 

 it was found that where the hills were dressed no early lice appeared, 

 but the rest of the garden was infested. 



It is thus pretty clear that this aphis lives in two ways during 

 the winter upon the prunes in the egg stage, and a few in the hop- 

 hills and other shelter, and thus living entirely upon the hop ; 

 damage being done to both host plants. 



[F. E. 



S3. OVIPAROUS FEMALE OF THE HOP- 

 DAMSON- APHIS FROM DAMSON. 



(Greatly enlarged.) 



DESCRIPTION OF THE APHIS. 



(1) Apterous Viviparous Female. On prunes, oval in form ; 

 bright to yellowish-green, with a central dorsal deep green line, and 

 a deep green jagged lateral stripe on each side. The frontal tubercles 

 distinct. Eyes, reddish. Legs and antenna?, apple green. Length 



