?O O. E. PLATH. 



osus, and, judging from the oviposition of the members of the 

 genus Bremus, is rather improbable of any of the Psithyri. The 

 observations of Sladen ('12) and of the writer also indicate that 

 Hoffer's ('88) surmise that the Psithyrus larvse, at least those 

 recently hatched, devour the larvse of their host, 1 is not true of all, 

 if of any, members of the genus Psithyrus. 



Six of the eggs laid by the Ps. laboriosus queen developed into 

 queen larvse which spun their cocoons about August 2$. On Sep- 

 tember 7, a Ps. laboriosus queen emerged from one of these. The 

 queens in the other five cocoons were heavily parasitized by Melit- 

 tobia sp. and did not hatch. Nor did any of the Bremus eggs and 

 larvse develop which were present in the nest when the Psithyrus 

 queen gained admittance to this colony. Whether or not, in this 

 case, the Bremus queen laid any eggs 2 after the appearance of the 

 Psithynis, could not be determined. 



Hoffer ('88, pp. 104, 105) states that whenever the old Psithyrus 

 queen dies, while her larvae are still very young, the latter, as a 

 rule, likewise perish, and he considers it probable that the Psithyrus 

 queen forages and contributes something to the support of her off- 

 spring, at least during their early larval stages. The latter is not 

 true of PsitJiyrus aslitoni, and, as the observations of Sladen ('12, 

 p. 6s) and of the writer indicate, is also improbable of other 

 species. Both the Ps. laboriosus and the Ps. aslitoni queen were 

 always at home, and, as regards the latter, foraging was out of the 

 question. She was able to fly but a few feet at the time the affinis- 

 ashtoni colony was taken, and still her brood, including some 

 newly hatched larvae, was in a flourishing condition. It is prob- 

 able, therefore, that the PsitJiyrus larvse which Hoffer ('88) had 

 under observation died from other causes. 



The behavior of the Psithynis laboriosus queen and the vagans 

 colony to each other was the same as that of the members of the 

 affinis-asJitoni colony, except during the first three or four days. 



1 This is true of the larva of certain solitary parasitic bees, as Verhoeff 

 ('92), Hoppner ('04), and Graenicher ('05) have shown. 



2 Sladen ('12, p. 69) claims that a large number of workers in a Psithyrus- 

 ridden colony become fertile. This was true of my queenless B. impatiens 

 colonies, but none of these would accept a Psithyrus queen. However, in my 

 Psithyrus-iniested colonies, all of which possessed the old Bremus queen, 

 none of the workers took to egg-laying. 



