INVESTIGATIONS ON THE MUTILLID WASPS 13 



M. europuea Linnaeus is found generally distributed in the nests 

 of a number of species of bumblebees in Europe. It is rather 

 remarkable that none of the American bumblebees have been found 

 to be parasitized by Mutillids. Certainly many more species of 

 bees and wasps in America are parasitized by the Mutillids than 

 we now know. In the case of those species of bees and wasps that 

 nest in colonies it should be a comparatively simple matter to 

 discover the Mutillid parasite, if one exists, on account of the con- 

 centrated numbers of the host. The cocoons of the host in such 

 cases can be collected in fairly large numbers and reared in the 

 laboratory, and during this procedure the parasite will nearly always 

 be discovered. In addition there will often result a correlation of 

 the male and female of a single species of the parasite which may 

 have been previously known as two species. It is to be hoped that 

 many of these potential Mutillid hosts may be investigated in the 

 future. 



So far the only hymenopterous insects found as hosts of Mutillids 

 are the various species of wasps and bees. Andre (1902Z/) has sug- 

 gested the possibility that the ants may serve as hosts in some cases 

 but this has never been verified. The field of investigation here 

 is a large one and the possibilities almost unlimited because so much 

 remains unlmown, and the hosts that are Imown are distributed in 

 at least three orders. 



TYPICAL LIFE HISTORY OF A MUTILLID WASP 



From the facts that are available due to the efforts of Drewsen, 

 Hoffer, Borries, Lamborn, Williams, and Ferton it is now possible 

 to formulate a typical life history of a Mutillid wasp. Such a life 

 history will not always represent the conditions in each specific 

 case but will serve as a type which can be modified more or less to 

 suit individual cases. This typical life history is as follows: 



1. Host: Coleoptera, Diptera, and Hymenoptera (either fossorial 

 wasps, social wasps, solitary bees, and social bees). 



2. The host is attacked in the prepupal or pupal stage, after its 

 cocoon has been spun, or the puparium formed. The host is then in 

 a quiescent stage and apparently the Mutillid does not paralyze the 

 host with its sting. [This does not include the Methocas, which are 

 not considered Mutillids (s. str.).] 



3. The female Mutillid penetrates the cocoon or puparium with 

 its ovipositor and deposits the egg, either by attaching it to the host, 

 or to the inner wall of the cocoon. Occasionally two eggs may be 

 laid in the same host cocoon. 



