CADDIS FLY LARVAE—FLINT 481 
The separation of the larvae of certain species in this group, especially 
of vboxr and invaria, is not at all satisfactory. 
The larvae agree on the following characteristics: head long and 
narrow, generally about 1% to 2 times as long as broad, and at most 
only slightly widened posteriorly. Second segment of maxillary 
palpus about twice as long as first; left mandible with 2 apical teeth, 
right with 3, of which mesal one is longest. Anal proleg without baso- 
ventral hook and apicolateral spur, although short processes which 
are not free of the membrane are present at both places; claws with 
ventral teeth. 
Rhyacophila vibox Milne 
Ficure 8,d 
Rhyacophila vibox Milne, 1936, p. 101 (male and female genitalia).—Ross, 1944, 
p. 36 (male and female genitalia, larva). 
Rhyacophila torva (nec Hagen) Vorhies, 1909, p. 713 (larva, unquestionable 
vibox). —Lloyd, 1921, p. 114 (larva, probably viboz). 
Adults of vibor are known to occur in many of the Northeastern 
and North Central states: Illinois, Michigan, Massachusetts, New 
Hampshire, New York, Ontario, Quebec, Vermont, and Wisconsin. 
The larvae of this species were reared and described by Ross, who 
furnished a determined series of larvae for study. The larval descrip- 
tion of Vorhies closely matches the larvae here described; furthermore, 
no other species in this group is known to occur in the North Central 
states. The description of Lloyd, who worked around Ithaca, N.Y., 
is of the larvae of either invaria or vibox, and inasmuch as vibox was 
collected near Ithaca, the description is assigned here. In any case, 
neither description is of the larva of torva, but of a species near viboz. 
The larvae of vbox are extremely similar to those of invaria. The 
characters here used for their separation may not hold when more 
material becomes available. It seems that the larvae of wibox have 
the dark shading continuous to the oral margin of the frontoclypeus, 
and the anal claws rarely have a second small ventral tooth. 
Description: Length, 16 mm. Head, brownish yellow, darker 
centrally and anteriorly; muscle scars faintly indicated by pale spots 
posteriorly; head capsule slightly broadened posteriorly; fronto- 
clypeus with posterior portion slightly elongated so that arms of 
frontal suture meet at slightly less than 90° (like fig. 8,a@); second 
segment of maxillary palpus twice as long as first; left mandible with 
2 apical teeth, right with 3 apical teeth, mesal one longest (like fig. 
11,6). Thorax, pronotum brownish yellow, a slightly darker oval 
spot posteromesally; fore femora considerably broadened. Abdomen, 
anal proleg with short basoventral and apicomateral processes, 
neither free of membrane; claw only rarely with a small second ventral 
tooth (fig. 8,d). 
