230 ILLINOIS ACADEMY OF SCIENCE 



ECONOMIC IMPORTANCE OF DIPTERA 

 J. R. Malloch, University of Illinois 



No other order of insects equals the Diptera in diversity 

 of habits in larval and imaginal stages. Many of the families 

 are largely beneficial, but unfortunately the good done by them 

 is counterbalanced by the injury inflicted by others. The es- 

 sentially phytophagous families, that is those families of which 

 the great majority of the species feed upon plants, are very 

 greatly outnumbered by those that are scavengers or preda- 

 ceous or parasitic. If we exclude those that are fungivorous, 

 only four families remain that can be classed as even prepon- 

 derating^ phytophagous — Cecidomyiidae, Trypetidae, Agro- 

 myzidae, and Chloropidae; a few of these are predaceous. It 

 must be borne in mind that a phytophagous species is not 

 necessarily injurious from the economic standpoint, as many 

 species feed upon and keep in check noxious plants and may 

 therefore be regarded as beneficial. 



It is but a step from the phytophagous to the scavenging 

 habit, and in Drosophilidae we find species that may feed 

 upon Cruci ferae, mining the leaves, or in sap exuding from 

 trees and in vegetable refuse. A great majority of the scav- 

 engers, however, rarely feed upon living plants, the only 

 other exception being those that are fungivorous. There are 

 eight families that may be considered as essentially fungivor- 

 ous — Macroceridae, Bolitophilidae, Platyuridae, Mycetophili- 

 dae, Sciaridae, Platypezidae. Phoridae, and Drosophilidae. 

 Many of the Sciaridae occur in decaying vegetation, while the 

 habits of Phoridae are remarkably diverse, some being true 

 entoparasites. 



The scavengers belong to more than a score of families. 

 In Muscidae all the species are scavengers; but in some other 

 families, Anthomyiidae, for example, we find phytophagous 

 and inquiline species, though these are greatly in the minority 

 and the family is essentially one of scavengers. The Sarco- 

 phagidae include some species that are true entoparasites, but 

 the great majority are feeders upon decaying animal and veg- 

 etable matter. The scavengers are in the great majority of 

 cases really beneficial, transforming dead animal and vege- 

 table matter into such forms as can be utilized by growing 



