LIl'^E-niSTOKV OK TIIK LAUV-BUfD UEKTLK. 477 



there is little or no migTation, that hibernation takes place 

 locally, and that the varieties bi-eed true ? Or, does the particular 

 environment allow only certain varieties to survive ? 



Two, possibly four, factors juive to be considered in a genetic 

 study of the Black and Red forms : — 



1. Pattern : that is, the shape and distribution of the spots. 



2. Colour: (a) black, which is the same in both "type "and 



black varieties ; 

 (^>) red, which, coiitrary to accepted opinion, I believe 

 difi'erent in the Red and Black forms. 



3. Size : there is great range in size in the Coccinellida% which 



Johnson believes is chiefly adaptational, but the mean size 

 of the varieties under consideration is difterent, and perhaps 

 constitutes a definite character. 



4. There may be a physiological factor in the reaction of these 



varieties to heat. 



Microscopical examination by transmitted light shows that the 

 reddish colour in both varieties is due to a clear yellow, to which 

 brownish-i-ed, semi-transparent particles are added in the Red 

 form and red-brown and carmine in the Black variety. 



There is probably a ])hysiological factor to account for the 

 seasonal appearances of the two forms, in England the Black 

 usually appearing later and disappearing eailier than the Red. 

 I have also observed that when the breeding-boxes were over- 

 heated, the Black could \[\e at a higher temperature than 

 the Red. 



2. IVie Food and Feeding of Adalia bipunctata. 



There is considei'able difficulty in feeding Adalia with its food, 

 living aphis. The occurrence of aphis is very erratic, being much 

 affected by sudden climatic changes, such as cold, wind, and heavy 

 rains. At times they disappear inexplicably. 



Adalia will eat many but not all species of aphis. ].")uring two 

 years' breeding I have found three species which a.re not accept- 

 able : — (1) Aphis rumicis, the black bean aphis which is found on 

 broad beans in early summer. The young of this species are 

 eaten to a small extent, l)ut the large only under stress of circum- 

 stances. One may continually find a bea,n-row black with this 

 destructive a})hid, but very few lady-bii-ds upon them when, on 

 a bed of nettles a few yards away, can be found large numbers 

 of Coccinellida^ — C. sepiempunctata, G. variabilis, A. hipuiictata, 

 Hahjzia '[A-gnttata, II. 12-pibnctata, and II. l^-pnnctata, — even 

 wdien the aphids are not obviously numerous. (2) A bluish-green 

 aphis (Macros iphuvi aconiticvi (Van <ler (loot)), which. 1 have 

 found only on Monkshood. This has never been eaten by Adalia. 

 Johnson says "several of the highly-coloured a.phis cannot be suc- 

 cessfully fed to Uoccinellids." (3) Ili/alopferus j)7'it,ni: this aphis 



