1970] 
Eberhard — Fungus Gnats 
369 
means of peristaltic contractions whichs originated in the trailing 
segment (s) and moved toward the leading end. A band of slime 
was laid on the silk when one of the fleshy segments came in contact 
with it, so as the larva moved forward, it left a slime trail behind it. 
A dendritic network of slime trails extended to all parts of the 
sheet, and the larvae always followed trails as they moved about. 
A peculiar method of turning around (also noticed in the myceto- 
philids L. walkeri by Madwar 1937, Platyura nigricornis by Mans- 
bridge and Buxton 1933, and Sciophila sp. by Osten Sacken 1886) 
enabled them to remain on a slime trail at all times without con- 
structing any circular trails: they turned the head 180°, and crawled 
back along themselves, advancing all segments simultaneously so that 
the head moved along the back or side in what had been the posterior 
direction while the tail continued to move forward until the turn 
was complete (see Fig. 4e). The function of the slime trails is 
not clear. 
While spinning and feeding, the larvae moved their anterior four 
segments without moving the rest of the body. Larvae ate holes in 
their sheets by moving their heads slowly in arcs in front of them- 
selves. The sheet was broken where the head touched it, and the 
portion inside the cut was ingested as the head swung. A part of 
the head capsule (the mandibles?) moved rapidly as the silk was 
cut. The rapidity with which the silk disappeared suggests the larvae 
probably used a silk-digesting enzyme. The alimentary canals of 
several dissected specimens were full of spores but contained no 
visible traces of any other solid matter, indicating that the larvae 
usually ingest nothing other than their sheets and their contents 
and rapidly digest the silk. 
Usually a larva immediately filled each hole it made in the sheet, 
swinging its head and segments 1-4 rapidly from side to side in a 
complicated pattern (see below). A new mat of silk lines running 
in several directions across the hole in the sheet was produced by 
these spinning movements. The new lines were almost always at- 
tached to the edges of the hole in the sheet rather than to the surface 
of the fungus. Silk eating was always preceded by a semicircular 
sweep (see description of spinning movements below), and was 
always followed by spinning activity. Semicircular sweeps were not 
always followed by eating, however, and larvae on sheets often spent 
periods of time spinning but not eating. 
A larva often concluded a series of spinning movements by placing 
its anterior end against the sheet and moving its whole body back- 
