PSITHYRUS CAMPESTRIS 217 



Antennae long ; length of flagellum 6^ mm. The 4th 

 joint of the antennae is very slightly shorter than the 3rd : 

 the 5th joint is almost as long as the 3rd and 4th 

 together. 



Armature distinct. 



A light male from Chobham, Surrey, in the Saunders' Collection, 

 has the whole 2nd segment yellow with the exception of a few black 

 hairs on its sides. 



Ps. campestris is widely distributed in England, 

 Wales, Ireland, and Scotland, and common in a few 

 places. In the Dover district it is seldom seen. 



Most authors state that it is parasitic on B. 

 agrorum, and its distribution points to this. In 

 Styria, Hoffer found it breeding in the nests of 

 B. agrorum and B. helferanus. 



Ps. campestris, like Bombus ruderatus, is subject 

 to colour dimorphism, most examples being either 

 very light or very dark. 



Judging by the large number of specimens I 

 have seen in Irish collections this is the commonest 

 species of Psithyrus in Ireland. In the lightest 

 Irish specimens the thorax is yellow with the ex- 

 ception of a few black hairs in the centre. None of 

 the numerous black specimens of both sexes from 

 Ireland that I have seen have lacked yellow, or a 

 trace of it, on the tail. 



