30 



are only comparatively few others count them in several 

 hundreds. But it has now been proved that they are cu- 

 ckoos and we know from other corresponding cases that 

 parasites vary extremely in size according to the quantity of 

 food they have had. It is further known that the strength 

 of the punctuation as well as the clearness of the colour 

 varies with the size of the specimen, and on these characters the 

 authors have based most of their species. It has further been 

 mentioned by various authors that the same species of Sphecodes 

 has been observed flying with different species of Halictus repre- 

 senting the larger as well as the smaller species: Ferton even 

 observed a large Sphecodes trying to widen the entrance of 

 the nest of one of the small Halictus, as it was too narrow 

 for it to get through. It is my opinion that the extent of 

 the variation of these insects is explained by the fact that 

 when specimens of the same species lay their eggs in the 

 cells of bees of very different size, a number of different 

 forms will be developed representing a continuous series from 

 the smallest forms of Sphecodes with weak punctuation and 

 obscurely coloured to the largest with strong and coarse 

 punctuation and clear colour. The before mentioned S. gib- 

 bus, var. wich deposits its eggs in the cells of the large 

 Halictus quadristrigatus is nearly double the size of the or- 

 dinary S. gibbus which are cuckoos with the middle-sized 

 Halicti. 



It is not my meaning to say that there is only one 

 single true species of Sphecodes, but how many species the 

 genus really contains is a question which cannot be ans- 

 wered by examination of dead specimens in the collections, 

 but only by studying their life history. 



