SOCIAL PARASITES 



fighting. There is little sign of loss of the tools used in nest- 

 ing, such as occurs in cuckoo bees, though the shape of the 

 mandibles is thought to be less suited to the manufacture of 

 paper. The cuckoo wasps have no workers. 



It is curious that V. austriaca is a short-headed wasp and 

 lives with a short-headed host, V. rufa, whereas the two other 

 cuckoo Vespula are long-headed wasps and live with long- 

 headed hosts. Yet all three cuckoo species show similar 

 changes in head-shape which must have been acquired inde- 

 pendently as a result of their mode of life. 



Our knowledge of how the cuckoo wasps establish them- 

 selves in the nest of the host is still very fragmentary. The 

 most extensive observations are those of Weyrauch in 

 western Germany. The cuckoo queens come out of hiber- 

 nation a good deal later than their hosts, and attempt to enter 

 the nest at about the time that the first comb of queen cells 

 is being constructed. At some point, perhaps when the 

 cuckoo begins to lay, a big fight ensues with the workers, 

 many of which are found dead in or near nests containing a 

 cuckoo queen. The host queen may survive for a time, but 

 apparently is killed or dies before long. Eventually, the combs 

 produce some workers and a few males of the host, but no 

 young host queens. Most of the later brood consist of young 

 queens and males of the cuckoo wasp. 



Amongst the wasps of the genus Polistes also, there are 

 three cuckoo species in western Europe. Their existence was 

 hardly suspected until it was first established by Weyrauch 

 in 1937. More detailed studies were published in Switzerland 

 by de Beaumont, in 1945. All the species have a characteristic 

 groove on the mandibles, due to a thickening of the upper 

 and lower margins. This, together with certain other features 

 of the head, are thought to be useful in fighting, but the 

 cuckoo Polistes are less different from the industrious species 



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