A NUTRITIONAL STUDY OF INSECTS 47 



teriae (type 'Y') and B. typhosus. The fl}^ eggs were sterihzed 

 by washing in 3 per cent lysol for two to three minutes. The 

 pupal contents were plated and found usually to be sterile. Teb- 

 butt does not mention the fact that the larvae probably obtained 

 their nourishment from the bacteria. 



From these experunents it appears very probable that the 

 larvae of Musca domestica feed on microorganisms and are as- 

 sociated with them in the same manner as Drosophila and yeasts. 



4. Experiments with a mycetophagous insect, Sciara, and a mite, 

 Tyroglyphus, living in decaying wood 



a. Experiments with Sciara. Through the courtesy of Mr. 

 A. M. Wilcox who turned the material over to me, I was enabled 

 to work on another fungus-eating insect found in twigs of the 

 mountain ash apparently affected by 'black knot' or some dry 

 black-rot disease. Under the bark and in the cambium of the 

 wood slender white worm-like larvae, 12 to 15 mm. long, with a 

 shining black head could be seen w^orking in a glossy gelatinous 

 sheath which they appeared to spin or secrete. As detemiined by 

 Mr. C. W. Johnson, the larvae proved to belong to a species of 

 Sciara, a genus of fungus gnats which feed in decaying vegetable 

 matter and are pests on cultivated mushrooms. 



The larvae were transferred to a medium of bran agar which 

 they infected with a mucor, a Gleocladium, and a Fusarium. The 

 larvae moved on the surface of the agar through the field of verti- 

 cal sporophores with their black globular sporangia overhead. 

 Occasionally one would raise its head and sieze a sporangium 

 between its mandibles. The disintegrating sporangia could also 

 be seen in the digestive tracts of the semitransparent larvae. The 

 mandibles are peculiarly fitted for such feeding, as they are quad- 

 rate in form and having three large and several small interlocking 

 teeth. The flat surface which the mandibles form would make 

 it impossible to seize any structure not raised above the surface 

 of the substratum. The larvae are also very fond of the mucilag- 

 inous secretions or exudations which appear as brilliant globules 

 on the sporophores or sporangium w^alls and as a sheath around 

 the larvae. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 28, NO. 1 



