392 
Psyche 
[December 
JEWELLED CADDIS-WORM CASES 
By Charles T. Brues 
During the summer of 1930 while collecting in the north- 
western part of Nevada, I secured some caddis-worm cases 
which have interested me greatly on account of a striking 
peculiarity evinced by these larval Trichoptera in selecting 
the minute stones that serve as material for covering their 
cases. 
We were returning from a sojourn in the far north- 
western, almost uninhabited, desert portion of the state, 
where permanent water is to be found at very few places. 
Reaching Fish Springs at dusk we decided to camp for 
the night close to the spring which furnishes sufficient cold 
water to form a tiny stream and a series of several small 
pools before it is absorbed and disappears in the soil. 
Examining the spring and short stream the next morning, 
I noticed in the blackish mud that numerous minute glisten- 
ing bits of opal flecked the dark background. It is not sur- 
prising to find opal at this place, as there are extensive 
deposits of opal and opalized wood in the contiguous country 
to the northeast, where the material is mined commercially. 
All the pieces in the spring were small or minute, but they 
emitted a brilliant pale blue fire. 
We collected a number of aquatic insects and noticed a 
concerted movement of the fiery opal flecks upon the bottom, 
which proved to be a caddis-fly dragging its case across 
the surface of the mud. Search revealed a number of others 
and finally we obtained nine specimens, each thickly jew- 
elled with bits of opal. As the amount of opal in the muddy 
bottom of the spring was far less in proportion to the other 
sandy or crystalline material than it is in the assortment 
utilized by the caddis-fly larvae, there can be no doubt that 
the brilliant color of the opal in some way influences the 
larvae in their choice. The cases are covered with sand, 
