314 THE AMEBIC AN NATURALIST [Vol. LIT 



and flowering plants. Only an extremely small, almost 

 negligible, proportion subsist upon ferns, so that from a 

 practical standpoint, we would include only those feeding 

 upon the Spermatophytes. This usage has developed on 

 account of the fact that the fungi which have many in- 

 sects feeding upon them, do not ordinarily engage t lie 

 attention of the economic entomologist, and for conveni- 

 ence it is acceptable in the present connection, as very 

 little is known concerning the specific hosts of insects 

 living in fungi. Furthermore, the food-plant is ordi- 

 narily understood to mean the species upon which the 

 larval or growing stages occur, for although it is com- 

 mon to find both the young and adult insects of the same 

 species subsisting upon the same plant, it occurs also 

 very frequently that the food of the larvae and imagines 

 of holometabolous insects is of entirely different nature. 

 Among the many other truly phytophagous insects living 

 in fungi are a number of families of beetles, for example, 

 which develop in the tissues of the larger, fleshy fungi 

 and many of these mycetophagous insects undoubtedly 

 show a very close association with certain species of 

 fungi. In addition, some insects subsist upon the lower 

 fungi, yeasts and even bacteria. The biology of these 

 latter is very imperfectly known in nearly all cases, 

 owing to the greater difficulties attendant upon studies 

 dealing with them. The well-known fungous-growing 

 ants and termites and the ambrosia beetles actually cul- 

 tivate certain fungi for food and other insects (undoubt- 

 edly a far larger number than is now known) subsist 

 upon various microorganisms, although they are, to the 

 eyes of the casual observer, feeding directly upon the 

 substrata which really nourish the microscopic fungi, 

 yeasts or bacteria, that in turn form the actual food for 

 the insects. As already said, however, these symbiotic 

 relations are in most cases only very poorly understood, 

 and they are entirely outside the scope of the present 



As distinguished from those of predatory, parasitic 

 and saprophagous habits, the phytophagous insects rep- 



