56 J. PERCY BAUMBERGER 



Undoubtedly these complicated habits have come about by 

 taking advantage of the enzymatic and possibly synthetic power 

 of the microorganisms. The type of association is the same as 

 with Drosophila, but is further compUcated by the physical prop- 

 erties of the wood and the habits of the insect. 



Some insects that feed on wood are apparently not associated 

 with any microorganisms, for the burrow does not appear to be 

 discolored. However, as a general thing, larvae are in symbiosis 

 with some microorganism when boring in woody tissue. When 

 feeding on leaves larvae are often completely or reasonably ster- 

 ile, and this is what would be expected from the foregoing as- 

 sumptions, for the tissue of the leaves is very soft and readily 

 digested. 



Portier ('05) has thrown some light on this subject by his 

 studies on the caterpillar of Nepticula, a small lepidopterous in- 

 sect that feeds in the parenchyma tissue of rose leaves. The 

 eggs are deposited on the leaf, which he supposes is sterilized by 

 the sun's rays, and the larva bores directly down into the leaf, 

 sealing up the entrance; the feces are not thrown out as in the 

 case of Tischeria. The exterior of the leaves were sterilized by 

 Portier and the whole leaf, with the excavation cut open, was 

 covered with bacterial media. The fifteen cases investigated were 

 perfectly sterile-- whereas all cases of species which throw out 

 the feces (Lithocolletis and Tischeria) were contaminated with 

 bacteria and fungi, especially Aspergillus niger. Later ('11 a) 

 Nonagria typhae larvae, that live in the trunk of Typha latifolia, 

 were investigated, and it was found that they were associated 

 with a pseudobacillus present in all tissues of the body, having 

 passed through the chitinous peritrophic membrane during ecdy- 

 sis. The bacteria were in all stages of decomposition in the 

 phagocytic cells of the blood. A second paper ('11 b) showed 

 that in Nonagria typhae a more complex situation exists than at 

 first described, in which two microorganisms are in symbiosis: a 

 micrococcus and a fungus Mucidium (Isaria) . This fungus must 



-- During the summer of 1917 I examined the digestive tracts of some thousand 

 Portlietria dispar caterpillars, pupae and adults, and found microorganisms pres- 

 ent only in pathological cases, therefore this insect is not associated with fungi. 



