404 Williani Morton Wheeler 



of life determine when the one kind ceases to be produced and the 

 other begins. The two types of individuals must, however, be 

 predetermined by alternative possibilities possessed by each egg. 

 The supernumerary or dwarf females differ from their large 

 wingless sister-forms, and from the young of the latter in a num- 

 ber of points. The shape of the body is entirely different and 

 resembles that of the sexual male; but it differs from the male 

 in two important respects; first, the dwarf mdividuals have a 

 very long proboscis which in this species is absent in the male; 

 second, there are no testes within the abdomen as in the males, 

 where they form a relatively enormous mass. Otherwise the 

 dwarfs are so similar in external form to the sexual males that 

 their true nature was uncertain until they were studied in serial 

 sections. These showed the absence of the testes and the presence 

 of rudimentary ovaries and ducts resembling those of miniature 

 parthenogenetic females. There was nothing to indicate that 

 the dwarfs could become sexual females. In fact the latter con- 

 tain each an enormous egg when they hatch." Morgan believes 

 that the dwarf females "are destined to a brief existence, and die 

 without progeny," and he gives good reasons for supposing that 

 they owe their origin to inadequate feeding of their parents. In 

 other words, we have here a case of alimentary castration differing 

 from that of the social Hymenoptera only to the extent that the 

 mother insect provides her egg with an inadequate amount of 

 ■yolk instead of feeding the larva from day to day on an insuffi- 

 cient amount of food. The resemblance of the dwarf females of 

 Phylloxera caryae-fallax to the workers of ants and other social 

 insects is very striking, although it seems not to have been 

 noticed by Morgan. 



Perhaps the well-know^n "high" and "low" types of male in 

 many insects, notably of the Scarabaeidae and Lucanidae are to be 

 regarded as the results of larval feeding. If this is the case, the 

 low males may present examples of alimentary castration. This 

 peculiar male dimorphism certainly bears more than a superficial 

 resemblance to the female dimorphism of the social Hymenoptera. 

 These may, indeed, be said to have high and low females, which, 

 like the corresponding forms of the opposite sex in Scarabaeidae, 



