Sept., '06] ENTOMOLOGICAL NEWS. 249 



Parasitic Hymenoptera of Algonquin Illinois. — V. 



By Wm. A. Nason, M.D. 



The present paper concludes the series cataloguing the 

 Parasitic Hymenoptera of Algonquin, Illinois. Altogether, 

 there have been listed 608 species and 10 varieties, under 252 

 generic names. The following table shows the number of 

 genera, species and varieties belonging to each family : 



252 608 10 



These parasitic forms of insect life are all dependent upon 

 their hosts for maintainance and perpetuation, and this point 

 of view opens up a most interesting subject of study. The 

 hosts are largely vegetable feeders, and consequently the flora 

 of the regions they inhabit must of necessity, to a great ex- 

 tent, be made up of the plants which furnish them suitable 

 food. All plants and plant societies are dependent upon the 

 existence of suitable soil, and climatic conditions for their 

 growth and continuance. Hence, we must consider, in order 

 to arrive at an intelligent idea of the origin and distribution of 

 these parasitic forms, what are the ecological relations of the 

 regions which control the vegetation necessary to perpetuate 

 these hosts. 



To do this it is best to first consider the geographical rela- 

 tions of these insect forms, and then the ecological conditions 

 of the fauna and flora of the regions occupied by them. The 

 first object may be first attained by consulting lists of species 



