LIFE-HISTORY OF THE LADY-BIKI) BEETLE 



485 



September 1919. Early in 1920 be visited this place, aiid found 

 large numbers of the insects lying massed npon one anotl er in 

 the cracks between the bricks where there was practically no 

 shelter. The Lady-birds w^ere on all sides of the chimney. 



In September 1919 large numbers of sej^tempnvctata were 

 reported from various parts of England, but in Stafibrdshire 

 there were at the same time large numbers of hipimctata and 

 C. W-jmnctata^ which, on account of their small size, were much 

 less obvious. This abundance was entirely accounted for by the 

 weather-conditions. Early in August there had been a, period 

 of warm fine weather during which aphis and Ccccinellid larva? 

 flourished : this was succeeded by a wet, cold period, which no 

 doubt retarded the pupae ; but when a, second period of hot 

 Aveather supervened, the retarded pupae responded, as my breeding 

 experiments show they will do, and simultaneously, instead of 

 over a protracted period, the adults appeared. 



4. llie Geneiical Relatiovs of the Varieties. 



Matings were made during the summers of 1918 and 1919. 

 During the first year, only 22 of the 57 fertile matings produced 

 a complete generation, the family in each case l)eing reduced to 

 one imago. In 1919, 23 complete generations were produced 

 from 35 matings. 



Eleven of these successful matings were Red x Red, and with 

 the exception of one, Mating 32, produced only Red ofiTspring, 

 among which there occurred small variations from their parents 

 and from type." The Red bred true, producing none of the 

 Black variety. 



The exceptional mating (32) consisted of two Reds taken w lven 

 mating. The female laid one small liatch of eggs (7), from which 

 two Black imagines were produced. Clearly the female was at 

 the end of her productive period, and had probabljMiiated with a 

 Black before she was caught. 



Six matings of Black x Black were made, five of which pro- 

 duced both Red and Black imagines, a phenomenon quite 

 different from the Red x Red matings ; but as it was not possible 

 to guarantee that the females had not had partners previous to 

 the scheduled one, it cannot at present be deduced that the 

 genetic constitution of the Black as regards the purity of the 

 o-enes is different from that of the Red. 



The sixth mating (24), wdiich produced only Blacks, was as 

 follow^s : — (S var. 4-maculata X ^ 4-maculata produced five 

 4-maculata and one 6-pustulata. The female had certainly had 

 no previous mate. 



The five matings of Black x Black produced 8 Blacks and 

 4 Reds. It must be noted that these Reds were all variations 

 from "Type" and not exactly like the Red parent. The problem 

 therefore arises — are these variations hetei'ozygous forms with an 

 intermediate appearance ? Similar varieties have, however, been 



