APID.E. 361 



sumed by tbe next morning ; more workers continually 

 hatch, out, and after a time the new males and females 

 begin to emerge. The last eggs laid by the ? produce 

 males ; the older workers also lay eggs as the season 

 advances, which always develop into males. 



The number of individuals in a colony varies much, the 

 colonies of the underground builders being the most 

 numerous on the average in this respect. Smith says that 

 the communities of terrestris are the largest ; a nest of 

 this species taken in August contained 35 ? , 20 (J , and 

 160 C , the majority of males and females had probably left 

 the nest ; in another nest he found 107 cJ, 560 ? , and 180 

 $ . The nests of the surface builders, according to the 

 same authority, contain only about half as many individuals. 

 The behaviour of the bees on their nests being disturbed 

 varies according to the species : terre><tris, typical form, and 

 lapidarius, especially the former, resent the intrusion vigor- 

 ously, flying round the heads of their disturbers, and doing 

 their best to sting them ; muscovum, sylvarum, etc., on 

 the other hand, appear to be terrified, and simply lie on 

 their backs, trying to sting anything which comes near 

 them. The species of Psithyrus, as stated under the head- 

 ing of that genus, occur in the nests as inquilines, and 

 species of the Dipterous genera, Vohicella and Conops, are 

 parasitic on Bomhus. Mutilla europiea occurs also in 

 some nests, but very little is known of its parasitic habits ; 

 various Coleoptera also are found, which come probably for 

 the food obtainable from the wax and honey. A species of 

 Acarus also infests the nests, feeding on the wax, and 

 sometimes swarming on the bodies of the bees and amongst 

 the eggs. 



The species of Bomhus are exceedingly difficult to distin- 

 guish apart, the colour of the pubescence varies so greatly 

 in different specimens of some species that it is wise to 

 rely only on structure as a character in the discrimination of 

 the species ; these characters are often very obscure, and 



