374 ENTOMOLOGY 



Mycetophaga. Many, though not all, of the fungus flies (Myceto- 

 philidae) feed on fungi. Larvae of a species of Sciara that feeds in woody 

 tissue were found to contain in the digestive tract fungous mycelia 

 along with considerable woody material. Larvae of the same species 

 were reared on a medium of bran-agar, which they soon infected with 

 molds, upon which they were subsequently observed to feed. The 

 wood is merely the substratum in which the food material develops. 

 (Baumberger.) 



The ambrosia beetles, of which there are many species, make their 

 tunnels in damp wood of weak or dead trees. Their food is not wood, 

 however, but a fungous growth which develops rapidly on the walls of 

 the galleries so rapidly often as to choke the galleries and kill their 

 inmates. The fungus begins its growth on a bed of chips which the 

 female prepares, and on which she lays eggs. The fresh tender growth 

 of the fungus is food for both larvae and beetles, but only the latter can 

 eat the older growth. " Different species of fungi are associated with 

 different species of beetles, and these associations are constant for the 

 same species in spite of changes of host plants." (Baumberger.) 



In connection with this subject the elaborate fungus-gardens of 

 leaf-cutting ants and of termites should be recalled (page 295). 



Selection of Food.- Insects find food for themselves or for their 

 future larvae by means of the senses of (i) smell, the most widespread 

 method; (2) taste, as with butterflies, pomace flies, flesh flies and other 

 forms that feed as adults; (3) vision, as with dragon flies, which after 

 capturing their prey test it, however, and reject portions unsuitable as 

 food; also bees, which can discriminate between flowers of different 

 colors. 



Brues adds, in his paper on this subject, that the selection of food 

 plants by Lepidoptera depends also on (i) " Some attribute of the plant, 

 perhaps an odor but far less pronounced to our own senses than those 

 mentioned above. Species restricted to plants like- Leguminosae or 

 Violaceae may be considered in this category. Undoubtedly there is 

 some attribute of such plants which insects can recognize in a general 

 way and not as a specific characteristic of some single plant species or 

 genus. (2) A similarity in the immediate environment or general form 

 of the food plant. The effect of something of this sort is seen particu- 

 larly in oligophagous and also polyphagous caterpillars feeding mainly 

 on trees or shrubs, such as the gipsy moth, Cecropia moth, etc., and those 

 of certain species like some of the Arctiid moths that feed upon a great 

 variety of low plants. (3) Apparently chance associations that have 



