74 Zoologica: N. Y. Zoological Society [HI; 3 



One naturally infers that either the larvae must make the 

 cocoons of frass or the beetles must envelop the pupae with this 

 material, but observation shov^^s that both inferences are incor- 

 rect. The larva does, indeed, build the cocoon, but utilizes nei- 

 ther the frass nor the materials of old, abandoned cocoons in its 

 construction. I have not seen the earliest stages in the process 

 but it is evident that the larva selects a flat surface and begins 

 to build a wall around an elliptical area, which thus becomes 

 the floor of the cocoon. Little material is added to the wall 

 at the end of the ellipse compared with the sides, where the 

 material is built up as a pair of folds like those shown in Fig. 16a. 

 I have seen sevei'al cocoons that had been abandoned in this or 

 a somewhat more advanced stage, but on two occasions I was 

 able to observe the completion of the structure from a stage like 

 the one figured. Since in both cases the insects behaved in 

 essentially the same manner I shall describe only one of them. 



The larva was first seen working inside the cocoon in the 

 stage of Fig. 6a, but it soon came out, wandered away to a 

 distance of a few millimeters and, after careful search, bit off a 

 minute particle of the living tissue of the petiolar wall, avoidmg 

 any frass-covered surface, returned, entered the cocoon at one 

 end (left hand side of Fig. 6a), carefully masticated the particle 

 with its maxillae, while mixing it with saliva, applied it to the 

 border of one of the folds, pressed it into place, crept out of 

 the other end of the cocoon and went in search of another parti- 

 cle Then it returned, entered the cocoon as before and repeated 

 the building process. Excursions were made every few minutes 

 and within a radius of 8 to 10 millimeters from the cocoon. The 

 particles, which were selected with the greatest care and often 

 after what seemed like some hesitation, were very minute and 

 greenish when first bitten off but had become brown (by a pro- 

 cess of oxydation?) by the time they had been incorporated m 

 the walls of the cocoon. The particles were applied now to 

 one fold of the wall, now to the other so that the edges became 

 rather irregular (Fig. Gb), but as most of the particles were 

 added to the middle of the folds, they began to approach each 

 other Still, their growth was very slow, owing to the minute 

 size of the particles and the time consumed in their selection. 

 The larva labored incessantly, making trip after trip and choos- 



