126 
Psyche 
[June-September 
they turn dark when wetted, as does bark, and become light again 
upon drying. Possibly Phereoeca may be associated with mammals 
other then man. Bat roosts should be checked for the presence of 
larval cases. 
Case Form and Function 
The larval case of Phereoeca is flat, spindle-shaped in outline, 
open at both ends, silk-lined inside, and covered with sand and 
other small particles outside. It is constructed by the first instar 
larva soon after hatching, is enlarged by each successive instar, and 
after special modification, is used for pupation. Fully formed cases 
are 8-13 mm long and 3-5 mm wide. Once a larva has completed its 
case, it never leaves; all life functions (feeding, excretion, molting, 
pupation) take place within the case. When prodded from its case, a 
larva does not re-enter it, nor does it make a new one. It wanders 
about, does not eat, and dies in a day or two. Such larvae often walk 
right over their cases without seeming to recognize them. Larvae 
occasionally paused upon encountering the inside silk portion of 
cases which I had split open; however, after a few seconds of explo¬ 
ration, they continued wandering. Larvae placed into cases, through 
a slit made in one side, repaired the slit and continued to live in the 
case as if nothing had gone wrong. They also accepted the cases of 
other larvae as their own. 
The case is the same on both sides; it does not matter whether it is 
flipped over or not. The two openings are also identical, and the 
larva uses both. The case is widest in the middle permitting easy 
turn-around inside. Larvae behave as though they don’t notice being 
upside down until they poke their heads out of their cases. If the 
case is flipped over while the larva is withdrawn, it next appears 
upside down, withdraws into the case, swivels around inside, and 
reappears right-side-up. 
When disturbed, the larva withdraws into the case and seals it by 
pulling the bottom-most side up. Presumably this is done using the 
mandibles. If it is then flipped over, allowed to come out, and 
disturbed again, it pulls up the “new” bottom-most side (Figure 2). 
The closed ends are very difficult to open from the outside, but 
easily pushed open from within. They stay open when pushed open, 
and closed when pulled closed, because both positions are stable. 
This phenomenon can be demonstrated by pushing in the ends of a 
paper tube, such as the core of a paper towel roll. 
