THEIR RELATION TO EACH OTHER 109 



The order Lepidoptera contains no parasites and 

 very few species which, in the larval stage, are preda- 

 tory. In the adult stage the mouth structure of butter- 

 flies and moths precludes their feeding on other than 

 liquid food where they feed at all. A very few of the 

 larvae or caterpillars are predatory, feeding on scale 

 insects or plant lice. Generally speaking these insect- 

 feeding caterpillars are rare; but that of the little 

 Phycitid Lcetilia coccidivora is really a very effective 

 control for certain of the soft scales. It is a species 

 that belongs to the same series as the flour moths and* 

 meal moths, making the same sort of silken tube as a 

 home; only, instead of webbing together kernels of 

 wheat, etc., it spins up a mass of scales and feeds upon 

 the eggs or young even before they have issued from 

 beneath the mother body. 



In the order Diptera we have a very interesting 

 mixture of forms, including many that are of the high- 

 est importance as parasitic or predatory checks to 

 other species; but we are less able to limit these species 

 to certain families. Here we may have, in apparent 

 close relation, species that as larvae are plant feeders, 

 scavengers and true parasites; and there is nothing 

 in the adult which indicates the habit of the larva, 

 so far as our studies have yet carried us. Even in the 

 midges, which are certainly to be ranked as plant 

 feeders, there are a few that have been credited with 

 feeding on certain of the smaller plant lice. Among 

 the Culicidaz or mosquitoes there are a number of larvae 

 that are truly predaceous, and a few of them, like those 

 of Psorophora, are veritable wolves among the other 

 wrigglers. They have the same fault that I have 

 already deplored for other species : they limit their own 

 increase by feeding upon their brethren when other 

 wrigglers have given out. 



