No. r>:w] 



FOOD-PLAXTS AX I) IX SECTS 



317 



the manner of mutations, and it will, I think, be evident 

 that we should attribute these, at least in part, to chance 

 mutations or aberrations of instinct in the parent insects. 



Before dealing specifically with the selection of food- 

 plants, it is necessary to classify in a general way the 

 types of food-habits generally met witli in insects. Thus, 

 Router applies the terms Pantophaga to omnivorous in- 

 sects, Phytophaga and Sarcophaga to vegetarian and 

 carnivorous ones respectively and Xecrophaga and Cop- 

 rophaga to those living upon dead animals and excremen- 

 titions material. Among the Phytophagous forms he 

 would further distinguish monophagous and polyphagous 

 species on the basis of the number of food-plants which 

 they utilize. Although satisfactory so far as it goes, this 

 fails to include several categories commonly referred to 

 l>y entomologists and for the present purpose it can be 

 readily enlarged as follows : 



(Mierophaga ! (Xecrophaga) 

 )Myeetophagaf |Copro P haga} 



In this arrangement a distinction is made between 

 vegetarian species with a single food-plant (Monopha- 

 gous), those with several definitely fixed ones (Oligo- 

 phagous) and those with quite indiscriminate food-habits 

 (Polyphagous). On the other hand predatory species 

 (Harpactophagous) and cntomophagous parasites are 

 distinguished, as each form a very large and important 

 group. Many necrophagous and coprophagous species 

 really subsist on bacteria, fungi, etc., and these may 

 perhaps be better designated as microphagous and 

 mycetophagous. 



Among phytophagous insects, the polyphagous habit is 

 probably the most primitive and the monophagous one 



