184 Psyche [August 



Bremus fervidus belongs to the Diimoiicheli group and to the 

 Pocket-makers, and it therefore is among the representatives of 

 these groups that we should look first for species which are given 

 to honey daubing. 



As already mentioned, Bremus colonies are occasionally 

 infested by parasitic bumblebees of the genus Psithyrus. Ac- 

 cording to Hoffer (1888, p. 132), this sometimes occurs in almost 

 every second colony of certain species. Other Bremus species, 

 on the other hand, never harbor these parasites (Cf. Sladen, 

 1912, p. 257), and this, as the writer pointed out recently (1922), 

 also seems to be the case with Br em us fervidus. It can hardly be 

 doubted that the honey daubing habit of Brevius fervidus plays 

 an important role in keeping Psithyrus from breeding in its 

 nests. 



In his "Catalogue of British Hymenoptera" Smith (1855, 

 p. 210) makes the following statement in regard to the apparent 

 immunity of certain English Bremus species from Psithyrus 

 infestation: '"Although I have taken or examined a very large 

 number of the nests of Bombus [Bremus], I have only oc- 

 casionally met with the parasites [Psithyrus] in them; but 

 never in the nests of the brown bumble-bees." All of these 

 brown species to which Smith refers (agrorum, distinguendus, 

 helferanus, and rnuscorum), like Bremus fervidus, are Pocket- 

 makers. However, Hoffer (1888, p. 132) found that in Austria 

 two of these brown species {agrorum and helferaiius) are fre- 

 quently victimized hyPsithyr'us cam/pestris Panzer, and Wagner 

 (1907, p. 78) reports that in Kussia Bremus jnuscorum suffers 

 severely from the depredations of various species of Psithyrus. 

 Bremus distinguendus Morawitz, the other species mentioned by 

 Smith, is very similar to Bremus fervidus in structure,^ 

 coloration, and habit. It is also very closely related to Bremus 

 latreillellus Kirby^so that Morawitz (1881, p. 238) and Friese and 

 Wagner (1910, p. 75) merely look upon it as a variety of the 

 latter. According to Sladen (1912, p. 257), Bremus latreillellus 

 is not prej'ed upon by any species of Psithyrus; nor has any 



6Cf. Sladen (1912, p. 187) and Franklin (1912-13, I, p. 392). 



6Cf. Hoffer (1882-83, H, p. 72); Radowszkowski (1884, p. 77); Sladen (1912, pp. 184,187); 

 d Lutz (1916, p. 503). 



