168 J. K. BREITEXBl < 111 K. 



insects could possibly have been saved by entirely mass cultures, 

 crossed with stocks having low sterility or high fecundity. 



This rather incomplete data shows that apterous is a simple 

 recessive. That the majority of apterous females did not 

 produce offspring might be correlated with the idea that such 

 females have genital openings too small for the male copulatory 

 organ to enter. Another apparent fact is that sterility was 

 manifested throughout, which might be interpreted as being due 

 to the stock from North Carolina in which apterous originated 

 and in which all apterous matings \vere made. 



The wild North Carolina cultures, in which the apterous 

 insects were discovered, were dead by November. They always 

 produced a less number of progeny than any other wild stock 

 since sterile pairs were always common; however, the Texas 

 wild cultures continually produced a great number of offspring. 

 All wild stocks were kept from generation to generation by 

 mating one or five pairs each time. More pairs mated possibly 

 would have been sufficient to have preserved the North Carolina 

 stocks alive. This sterility could have been eliminated by 

 crossing apterous to the Texas cultures instead of the one in 

 which it arose, but was the only one present at this time. This 

 relative infecundity, further, accounts for the low number of 

 offspring discovered in these experiments. It is unknown to 

 which autosome apterous or sterility was linked, because no 

 crossover tests were possible. 



The average number of progeny produced per pair is the 

 lowest observed. Table I. for 50 pairs mated gives 198 offspring, 

 which is for each pair an approximate 1 : 4 ratio. For a com- 

 parative conception the following ratios are summarized from 

 another set of experiments: a 1 : 5 ratio for pure lines of white 

 body color and black spots on elytra, the R w s cultures; a 1 : 38 

 ratio for red body color and black spots on the elytra, the Rs 

 cultures; a 1 : 50 ratio for red body color and red spots on elytra, 

 the RS cultures; a 1 : 46 ratio for black body color and black 

 spots on elytra, the R b s culture; and, lastly, one wild culture, rs, 

 gave a 1 : 52 ratio. This wild culture is the highest of all in 

 giving a greater average of adults from each pair bred. 



It is about thirteen times more prolific than the apterous wild 

 stock from North Carolina. Aside from this extremely low 



