1921] Wheeler: Some Social Beetles 75 



ing every particle with the same diligence and avoiding the re- 

 mains of empty cocoons in the immediate vicinity, although 

 their materials, one vi^ould suppose, might have been easily ap- 

 propriated and quickly built into the cocoon under construction. 

 The two folds or side-walls slowly approached as the work pro- 

 gressed and eventually fused with each other, the larva always 

 entering at the same end, applying the particle to one of the 

 edges from the inside and leaving by the opening at the opposite 

 end. Then it set itself to building the walls around this latter 

 opening, which grew smaller and smaller (Fig. 6c), till the larva 

 could no longer squeeze through it and was compelled when 

 about to leave the cocoon to turn back on itself, bending its 

 body in a loop with the two limbs in contact, and crawl out of 

 the opening by which it had entered. This feat seemed to be 

 accomplished with considerable effort but had to be performed 

 after each particle had been built into the wall of the cocoon. 

 Eventually the small opening was closed and the cocoon had 

 only a single large elliptical orifice at one end (Fig. 6d) . The 

 larva now began to contract this orifice, but after a time, as it 

 grew smaller, the insect on returning, no longer entered the 

 cocoon and reversed its body in order to apply the particles to 

 the edge of the orifice, but merely thrust its head and a few of 

 its anterior segments into the cocoon and left the remainder 

 of its body outside. At such times it used as a support or ful- 

 crum a structure which I had not seen used at any previous 

 stage of larval life, namely, the proleg which terminates the 

 conical tenth abdominal segment. This structure is described by 

 Dr. Boving (Zoologica III, No. 7) and clearly shown in his figures 

 (PI. VII, figs 1 and 2). When the size of the orifice had been 

 reduced till the larva could only just squeeze through it, the 

 insect entered the cocoon, reversed its position and continued 

 building along the edges of the orifice with particles scraped 

 from the inner surface of the structure. The orifice thus soon 

 grew too small to permit the egress of the builder. (Fig. 6e). 

 Then the imprisoned creature slowly closed the opening and the 

 cocoon was completed (Fig. 6/). 



A few days after the larva has thus immured itself, it sheds 

 its cuticle and becomes a pupa which lies loosely in the cavity of 

 the cocoon and has the appearance of Dr. Boving's Plate IX, figs. 



