10 
Psyche 
[March 
Caddis larvse inhabiting movable cases have the head bent 
downward so that the mandibles are ventral (hypognathous) 
in position, the long axis of the head at an obtuse or even a 
right angle with the long axis of the body. Those with a 
right-angled attachment are said to be eruciform larvse, 
those with an obtuse angle to be suberuciform. Caseless 
larvse have the long axis of the head in line with the long 
axis of the body and the jaws hence at the anterior end of 
the animal (prognathous). Such larvse are said to be 
thysanuriform or campodeiform. 
Case-bearing larvse frequently have fleshy tubercles on the 
sides and notum of the first abdominal segment. These are 
called spacing humps, and serve to keep a passage for respir- 
atory water between the larva and its case. Such larvse also 
often have a prominent projection from the prosternum, 
extending between the front coxse. This is the prosternal 
horn or prosternal spine. 
The head capsule or epicranium splits at ecdysis into right 
and left halves. It bears the articulating surfaces for the 
mandibles antero-laterally and may or may not meet on the 
mid-line ventrally, anterior to the neck opening (occipital 
foramen). In some forms a submentum or gula is well de- 
veloped, the gula being sometimes quadrate, at other times 
triangular or crescentic. It may keep the epicranial halves 
entirely apart, extending from the labium to the occipital 
foramen, or it may separate them only anteriorly, so that 
the foramen is entirely surrounded by epicranium. A U- or 
V-shaped emargination in the anterior margin of the epi- 
cranium on the mid-dorsal line accommodates the frons to 
which the labrum is attached by a flexible membrane. There 
is no clypeus. The antennae are usually very small. 
Many larvse have a fringe of hairs along the abdominal 
lateral line, the so-called “lateral fringe The abdomen fre- 
quently bears along the dorsal, lateral and ventral surfaces 
filamentous or branched structures called gills, although 
their respiratory function is doubtful. Around the anus 
filamentous or sac-like structures are often seen. These are 
the rectal gills, which are seemingly retractible into the 
rectum. Also apical on the abdomen are the prolegs, fleshy 
structures with claws, used in locomotion. The thoracic 
appendages are true legs, and consist of five segments, a 
