48 J- PEECY BAUMBERGER 



As mentioned above, the larvae appear to move in a gelatinous 

 sheath over the wood. This habit has been observed in a number 

 of fungus-eating Diptera and has been described by many authors 

 as a secretion of the larvae. The following extract from Malloch 

 ('17) will illustrate the present interpretation of the habit: 



Nearly all of the larvae (Mycetophilidae) spin webs in the galleries 

 they make in their food; in the case of species that live externally upon 

 fungi the web is slimy, rather loose and irregular. I have paid particu- 

 lar attention to some species I have reared, and find that the larvae of 

 this group do not pass over the threads but through them as in a tube, 

 the body enclosed except anteriorly. The threads are slimy in nature 

 and the presence of the larvae may be detected by the glittering sur- 

 face of the fungus which appears as if a slug had crawled over it (p. 

 250). 



My larvae, feeding on mold in bran media, could be observed 

 very closely under the binocular microscope. It was seen that in 

 passing through the 'field' of fungus the larvae usually took a cer- 

 tain course, thus fomiing a 'runway' similar to that made by a 

 rabbit in high grass. The sporangia of mucors are converted into 

 a mucilaginous mass when the spores are discharged and the 

 sporophores also secrete a sticky fluid, both of which stick to the 

 surface of the larvae as they pass through the fungous growth. 

 Thus a shining gelatinous sheath is formed through which the 

 larv?.e pass. When moving over its course the larva 'flows' 

 along in a large drop of liquid which completely surrounds 

 the insect and assumes the same form. The surrounding 

 drop, if stained with eosine and examined under the 1.6 mm. 

 objective, proves to be a mass of spores of various kinds all 

 arranged as though embedded in a clear unstained substance. A 

 larva will often reach out and eat a portion of the surrounding 

 drop of another larva that is passing. The sheath when stained 

 shows a mass of mycelia growing from the spores embedded in the 

 gelatinous matrix of fungous mucilage. 



Brues ('02) has described the 'web' of Neoglaphyroptera opima 

 Loew\ and believes that it is spun by the larva which is found 

 under the bark of fallen trees. As the insect is quickly killed by 

 evaporation, he believes the web to be a protection against this 

 danger. The larva was described as at tunes moving its head 

 towards the web as though eating it. 



