62 THE HUMBLE-BEE 



in 



for the extra thick skin, many thick-hided animals 

 lacking hair. Their stings are stouter and more 

 curved than those of Bombus : it is interesting to 

 note that the sting in the queen honey-bee, who 

 also uses it for killing queens, is curved, while in 

 the worker honey-bee the sting is straight. 



The movements of the Psithyrus, whether flying 

 or walking, are lethargic and awkward. When 

 visiting the flowers in search of food she does not 

 travel systematically from blossom to blossom like 

 an industrious humble-bee, but settling upon a 

 bloom she sips lazily sufficient nectar to satisfy her 

 immediate need, and afterwards is very likely to 

 become drowsy. Fatigued by the exertion of 

 obtaining food for herself, she is plainly incapable 

 of the sustained effort that would be needed had 

 she to provide for the wants of her young. 



Whenever the weather is pleasant she searches 

 leisurely for a nest of the particular species of 

 Bombtis which it is her instinct to victimise. In 

 this work she is guided, like a dog, largely by 

 scent. In May 1895 I caught a searching queen 

 of Ps. vestalis and put her into a glass jar in which 

 I had kept some queens of its host, B. terrestris, 

 for several hours, so that the jar had acquired the 

 characteristic odour of this bee. The Psithyrus 

 queen ran about inside the jar in great excite- 

 ment, waving her antennae and stroking the in- 

 terior of the jar with them, apparently trying to 

 trace the path the queens had taken. After a few 

 minutes' hunting she flew out of the jar, but finding 



