29 



Resumé 



Notes on the Life History of Sphecodes. 



By 



J. C. Nielsen. 



It has always been a question of much argument whe- 

 ther the species of Sphecodes are cellbuilders or parasites 

 on HalictMs. Fargeau, ISmith, Herrn. Müller, Friese 

 etc. held to the former opinion whilst Perez, Perkins, 

 Fer ton etc. considered them to be true parasites. 



This question has presented so great a difficulty to 

 answer, on account of the uncertainty in following in the 

 ground the galleries of Halictus. Even the fact of finding 

 cells of Sphecodes in amongst the nests of Halictus would 

 by no means be certain proof that these might not belong 

 to separate nests of Sphecodes. The object therefore Avould 

 be to find a nest of Halictus forming a definite cluster of 

 cells and should amongst these cells be found one contai- 

 ning Sphecodes it would then prove that it was a cuckoo. It 

 is known that one species Halictus quadristigatus has this 

 peculiarity of building definite nests, and whilst I was dig- 

 ging for the nests of this species I gave particular attention 

 to notice w^hether specimens of Sphecodes should be found 

 with it. This Avas the case. A large species Sphecodes 

 gibbus, L. var. was fiying with the Halictus and followed 

 them into their burrows. When quickly unearthing a nest 

 where I had seen Sphecodes entering, I discovered it sitting 

 in a cell nearly filled with honey. Later on I found se- 

 veral cells containing larvae differing from those of Halictus, 

 and which can hardly be other than those of Sphecodes. 

 Finally I found in the autumn a cell containing a dead 

 specimen of a fully coloured Sphecodes pupa. It is therefore 

 proof that Sphecodes is a cuckoo with Halictus. 



Another question concerning this genus is how many 

 species it contains. Whilst, according to some authors there 



