28 O. E. PLATH. 



and Sladen ('12). Here. the question arises: What becomes of the 

 eggs laid by the Bremus queen, or workers, of a Psithyrus-ridden 

 nest? Hoffer ('88) considers it probable that the young larvae 

 which hatch from them are eaten by the young Psithyrus larvae. 

 However, Sladen ('12) actually saw a Psithyrus queen devour the 

 eggs of Bremus workers, and believes that she always disposes of 

 them in this way. He (p. 257) also thinks it is probable that the 

 race-suicidal habit of the workers of Bremus lapidarius Linnaeus, 

 which sometimes eat the newly laid eggs of their mother, is asso- 

 ciated with the parasitism of Psithyrus. He believes that the 

 workers which devour the eggs of their stepmother perpetuate this 

 instinct through their sons. In support of this theory, he states 

 that he has never seen the workers of Bremus latreillcllus Kirby, 

 " a species that is not preyed upon by any species of Psithyrus," 

 molest their mother's eggs. This explanation does not seem plaus- 

 ible. It is a well-known fact (cf. Wheeler, '10) that both queen 

 and worker ants, even of those species which are not molested by 

 parasitic ants, sometimes eat their own eggs. Moreover, the writer 

 has frequently seen the workers of Bremus fcrv'idus Fabricius eat 

 their mother's eggs, and this species, as will be shown in another 

 paper, probably does not suffer any species of Psithyrus to breed 

 in its nests, a view which is supported by more than twenty records 

 (10 by Putnam, "a large number" by Franklin, and 7 by the 

 writer) of fcrvidus nests, none of which were victimized by a 

 Psithyrus. 



The question has sometimes been raised as to whether or not the 

 members of the genus Psithyrus have any workers. Hoffer ('88, 

 p. 114) answers this question negatively. Among the 61 ashtoni 

 females reared by the writer there is a great variation in size (cf . 

 Plate I.), some specimens not exceeding that of medium-sized 

 affinis workers. It will also be noticed (cf. Plate I.) that the 

 Psithyrus males vary greatly in size. If it is true that the differ- 

 ence between queen and worker of the social Hymenoptcra is due 

 to a quantitative or qualitative difference in feeding during the 



varlabilis hatched from this colony. Four years later (June 24, 1884), one 

 of his sons discovered a nest of Bremus pratorum Linnaeus, containing the old 

 queen, 2 young queens, 5 males, and 26 workers of B. pratorum, and the old 

 queen, 9 young queens, and 4 males of Psithyrus quadricolor Lepeletier. 



