50 Trans. Acad. Sci. of St. Louis. 



The same kind of notes were made on 13 of the insects 

 from the large, fluffy cocoons in an attempt to detect any 

 points which might seem characteristic of this group. 

 (See Table 28.) 



Here we have 9 insects which mated normally, and all 

 but one yield a very small number of infertile eggs. "We 

 have also 2 females with the mating period prolonged 

 to 36 and 38 hours; here also is a very low per cent of 

 infertility. Then we have the opposite extreme, 2 which 

 were separated after only 6 and 2 hours in mating, and 

 even here the fertility is almost perfect. In the earlier 

 series of experiments we were afraid to cut the mating 

 shorter than 3 hours, but here a 2-hour period in copulo 

 seemed quite as sufficient for perfect results as a much 

 longer one. 15 On the whole, the insects from the fluffy 

 cocoons show a very slightly higher per cent of infertil- 

 ity than the normal Cecropias of this lot, but the influ- 

 ence of two extreme individuals is responsible for this. 

 This infertility, however, even if it were more than mere 

 chance of this material, could not be of any effect toward 

 the elimination of this variety (if these do constitute a 

 variety, with their own peculiar characteristics main- 

 tained by heredity), because, as we have seen in a pre- 

 vious chapter, they produce a larger number of ova than 

 do the normal Cecropias. Hence fluffiness is not corre- 

 lated with fertility, though it might be with fecundity. 

 In this lot we find a low proportion, 5%, of the fertile 

 ova which failed to produce larvae. This indicates that 

 this group of parents are a vigorous stock. We also see 

 in this lot no correlation between early and late oppo- 

 sition and infertility. 



For some undiscovered reason, the material of this 

 year shows a much lower per cent of infertility than did 

 the 1911 collections. Also in this lot we found no indi- 

 viduals which, after either a normal, prolonged or short- 

 ened mating, still had all of the eggs infertile as we did 



is See p. 61 for discussion of 1-hour matings. 





