INVESTIGATIONS ON THE MUTILLID WASPS 5 



sitic relation existing between M. euroyaea and the bumblebees, 

 proved that they were not social insects, and that they did not pro- 

 vision their nests with other insects as in the case of other fossorial 

 wasps. 



The hosts of a number of other species of Mutillids were discovered 

 following the work of Drewsen, It was found that the Mutillids 

 were not limited to bumblebees for hosts, but parasitized many other 

 species of bees and wasps. 



The observations of Christ, Dahlbom, and Drewsen indicated that 

 M. europaea was not limited to any single species of bumblebee as a 

 host, since Christ had observed Bombus muscorum Linnaeus, Dahl- 

 bom made his observations with BoTribus rajellus Kirby, and Drew- 

 sen's material was that of Bonibus seisms hiranus Kirby. 



Hoffer (1886) carried out many rearing experiments with bumble- 

 bee nests and reared M. europaea from the nests of 11 different 

 species of Bomhus. New points in the life history of this wasp 

 observed by Hoffer were as follows : 



1. The female Mutillid pierces the Avax wall of the cell, paralyzes 

 the Bombus larva within with her sting, and then deposits the ^g^. 



2. The Qgg hatches in three days. 



3. When full grown the Mutillid larva spins its own cocoon within 

 the cell of the bumblebee. 



4. The length of the pupal stage was estimated at 20 days. 



In addition to these he says that he did not observe any hostile 

 action on the part of the bumblebees when Mutillids entered their 

 nest for purposes of oviposition, and that he thought there might be 

 two generations per year of M. europaea. 



Borries (1892) gives an account of a species of Mutillid which has 

 a species of Crabro as a host and thinks it doubtful that the Mutillid 

 female stings and paralyzes its host, since the host larva is full 

 grown and has spun its cocoon before it is parasitized. In contrast 

 to Hoffer's statement that no hostilities were observed between 

 M. europaea and the bumblebees is the account of Melander and 

 Brues (1903) in which they describe the combats between Pseudo- 

 methoca canadensis (Blake) and Halictus bees. 



The most complete and detailed account of the life history of any 

 Mutillid is that relating to MutUla glossinae Turner, which has been 

 worked out in connection with the investigations on tsetse flies in 

 Africa. This wasp was first reported as a tsetse fly parasite by 

 R. A. F. Eminson (1915) as follows: 



In a batch of 258 collected Glossina pupae, from one puparium there emerged, 

 on the 21st of June, 1914, a wingless parasitic wasp of the genus Mutilla. It 

 was observed that the wasp on emerging had broken open the puparium in 

 precisely the same way as would the fly itself, so that a mere external exam- 

 ination of the case would not reveal the fact that the fly pupa had been 

 parasitized. On investigating a number of pupa cases collected in the field, 



