LOUISIANA CIRCULAR No. 6. 29 



its host is common in the State there is scarcely any doubt 

 but that it is there and can be found at the proper season. An- 

 other species of this same genus, occurring in Europe, is known 

 to have similar habits. 



There are a number of other species of Hymenoptera that 

 have been observed to be natural enemies of the horseflies, and 

 these, as well as the ones mentioned, should receive further study, 

 so that the benefits derived from them will be better understood 

 and the possibilities of utilizing them realized as far as possible. 



THE ROBBER-FLIES. 



These belong to the order Diptera, as do the horseflies. The 

 robber-fly known as Erax lateralis Macquart is common whera 

 f have been in Louisiana, and is a regular hawk among insects, 

 frequently rupturing the smaller members of the genus Tabanus, 

 as well as other insects. It does not appear, however, that the 

 robber-flies are of as much importance in this connection as the 

 wasps, for the reason that the adults do not attend their larvae 

 during growth, and hence capture insects for their own food 

 only. As the robber-fly larvae are predaceous and live in the 

 ground, they have an opportunity to capture other larvae that 

 live in such situations, and therefore they may devour an oc- 

 casional immature horsefly. 



There are scores of species of large flies belonging to the 

 same family us the one just named, and all of them procure their 

 frod in the same way that it does. They are cunning insects, re- 

 maining perfectly quirt in sonic inconspicuous place until an 

 insect that they desire for food comes close enough, when they 

 pound upon it and by means of their strong legs, which ar.- 

 provided with sharp claws, retain it until they introduce 

 their mouth parts and suck away its life-blood. Species of the 

 genus Deromyia were especially conspicuous in the fields in the 

 vicinity of the Gulf Biologic Station, and they were often seen 

 c.j pturiiiir horseflies for food. 



In a complete report on the natural enemies <>f horseflies. 

 the large dragon flies and various species of 1 lemiptera. or true 

 li'gs. should receive consideration. Spiders often catch the adult 



