66 BEES AND WASPS [cH. 



in late summer and early autumn; and there the 

 perfect insect remains underground and dormant 

 until April or May of the following year. They are 

 not infrequently brought to light by the spade or fork 

 in mid-winter. 



The Nomad bees of whom so many are "cuckoos '' 

 upon various species of Andrena might easily be 

 mistaken for small wasps, their colours being yellow 

 and black, or yellow and red. Although so different 

 at first sight from the usually sober-coloured Andrenas, 

 they present both in the pupal and in the imaginal 

 stages so many points of structural similarity to their 

 hosts that it is thought that they are a stock of 

 the Andrena family that has become decadent as the 

 result of disregarding the plain duty of every parent. 

 No entirely satisfactory explanation has yet been 

 given to account for the gay uniform of the Nomads : 

 it is possible that yellow and black is in evil repute 

 among insectivorous creatures, and that the compara- 

 tively defenceless Nomad her sting is a contemptible 

 weapon profits by the resemblance to really formid- 

 able or nauseous insects ; but it is impossible to feel 

 that this exhausts the question. A very curious 

 difference between the Andrenas and the Nomads lies 

 in their death attitudes : when killed by chloroform 

 an Andrena always bends its abdomen downwards 

 and forwards beneath the thorax, whereas a Nomad 

 killed by the same method always turns its abdomen 



