Pomona College, Claremont, California 159 



ing timbers; but, on the contrary, was always found working in the 

 sound wood. This, I think, is a wise choice, for one of its dangerous 

 foes is found abundantly, tunneling through decaying redwood. 

 The surface chosen for making an entrance is generally vertical or 

 slanting. When slanting or, as is sometimes the case, horizontal, 

 the under surface is always chosen. For a short distance the bur- 

 row takes a course nearly or quite at right angles to the surface 

 entered, then gradually changes to a course parallel to that surface, 

 and always (with very few exceptions) leads upward in the slanting 

 or upright timber. These tunnels vary in length from one inch to 

 twelve inches and are, as a rule, remarkably straight. I am at a 

 loss to know certainly what guides these interesting little carpen- 

 ters in the construction of so straight a tunnel. My first idea was 

 that they followed the grain of the wood, but in one case, where a 

 knot occasioned a decided curve in the grain of the wood, the tun- 

 nels had been constructed straight as usual (Fig. 7). The most 

 reasonable explanation seems to be that the vibrations of the wood 

 serve to indicate the distance from either surface, for when boring 

 in a plank only \x-inch thick they keep a line remarkably nearly 

 equidistant from the two surfaces and never have I seen where they 

 broke through to the surface. But a fact in the way of this theory 

 is that they sometimes make tunnels just as straight in a 2-inch 

 timber with the distance from one surface several times greater 

 than the distance to the opposite surface. It is an interesting point 

 which 1 have not yet solved to my satisfaction. My description 

 fits the majority of tunnels. In a very small percentage of the cases 

 studied, the tunnels were short and seemed to be in almost any 

 position. 



The excavation of these tunnels is evidently a laborious task, 

 though the little creatures ply their trade with great avidity, and 

 while at work they are not at all easily disturbed. The writer 

 watched one of these patient workers for three hours, during which 

 time she kept her mandibles working away continuously, leaving her 

 work only twenty-five minutes, evidently for "lunch," after which 

 she returned to resume her task. By closest scrutiny 1 was unable to 

 see that the two and a half hours of labor had lengthened her bur- 

 row. T returned six days later to find her still vigorously pursuing 



