Ll. Lloyd 15 



average the duration of the first stage was 5 days, the second 2 days, 

 the third 3 days, and the fourth stage 8 days. On Ranunculus in February 

 and March with a mean temperature of 64° (range 45-94°) the duration 

 in days of the four stages in four scales was : 1st, 6-7 ; 2nd 4-6 ; 3rd 8-11 ; 

 4th 16-19. On beans in March and April, with a mean temperature of 

 67° (range 47-101°), the average duration in days of 49 scales was: 

 1st, 7; 2nd, 3; 3rd, 6; 4th, 12. These instances sufficiently show the 

 proportion of the larval life which is spent in the various instars. 



The emergence of the adults appeared to be always in the early 

 hours of daylight. 



6. OCCURRENCE OF A. SON CHI KOTINSKY IN ENGLAND. 



A second form of pupa appeared in the greenhouse where the main 

 culture of A. vaporariormn was kept (Plate I, fig. 2). This scale differed 

 from the typical form in the absence of dorsal tubercles and processes 

 and the greater development of the marginal waxen processes which 

 stuck out parallel with the leaf surface. It was first seen on a small Acer 

 which had been brought in to test its susceptibility to the fly and had 

 been in the greenhouse for some weeks ; later, on Brassica oleracea which 

 had been introduced for the same purpose. Both these plants were 

 thought to be cleaji at their introduction and the typical scales never 

 developed on them. It was also found on Polygonum, aviculare and 

 Sonchus oleraceus which had grown from seed in the chamber. Outside 

 it was found on Acer, Sonchus, Clarkia, Tropaeolum indicum and T. can- 

 ariense. Its incidence in numbers in the Station garden corresponded to 

 that of the typical A. vaporariorum, the experimental greenhouse being 

 the focus. The same scale was seen in Guernsey in October massively 

 infesting Sonchus in the greenhouses, again in association with A. vapo- 

 rariorum. A Polygonum which, after pocket-lens examination, was 

 believed to hold the atypical form only was cleared of all adults and 

 placed in a muslin cage with three tomato plants which were uninfested. 

 This cage was unopened for a month during my absence from the Station, 

 watering being done through the muslin. At the beginning of October 

 when the cage was opened there had been time for one generation to 

 breed through. The tomato plants were found to be massively infested 

 with typical A. vaporariorum in all stages. It was then thought possible 

 that the two scales belonged to the same species as no differences in the 

 adults could be detected. Material from the cage and from outside was 

 therefore submitted to Mr Laing of the British Museum who reported : 



"The absence of dorsal tubercles gives the form found on Acer, Tro- 



