2i6 THE HUMBLE-BEE vm 



5. PSITHYRUS CAMPESTRIS, Panzer. 



Queen. Medium sized ; length 1 7-1 8^ mm., expanse 

 35-38 mm. ; sometimes smaller. 



In light specimens the head is black, with a few yellow 

 hairs on top ; thorax black, with a wide yellow band in front 

 and a rather wide yellow band, often darkened, behind. 

 Abdomen black, with the sides of the 3rd segment (except 

 at the base), and the sides of the 4th and 5th segments 

 yellow. 



This species is very liable to darken : the yellow band 

 on the back of the thorax disappears first, then the front 

 band on the thorax, and lastly the yellow on the tail. 



Coat rather thinner, and the hairs slightly coarser and 

 stiffer than in any other humble-bee. All the segments of 

 the abdomen are almost bare in the middle. 



6th segment bare and shining, punctured towards the 

 apex. 



The elevations on the 6th ventral segment are rounded and 

 wide and together form a V-shaped mark, with a deep division 

 in the middle. 



Male. Length 15-16 mm., expanse 28-31 mm. 



In light specimens the head is black, with some yellow 

 hairs on top ; thorax black, with a wide yellow band in front, 

 and another wide one behind ; abdomen yellow, with the 2nd 

 segment black, but yellow at the edge except in the middle, 

 the 6th segment often black in the middle, and the 7th 

 segment black. The yellow on the 1st segment is 

 obscure. Cf. the male of B. latreillellus. 



In dark specimens the whole insect is usually black, with 

 the exception of the 4th and 5th segments which are deep 

 sooty yellow, interrupted in the middle with black. These 

 segments too are sometimes black. 



Hairs slightly coarser and slightly stiffer than in any 

 other humble-bee. The 6th ventral segment is slightly 

 channelled down the middle and bears on either side a tuft 

 of long black hairs. 



