[December 
294 Psyche 
tubercles which are more highly developed than in the case 
of the host. 
The average cocoon is 15 x 7.3 mm. (extremes 13 to 17 
and 7 to 7.5 respectively) ; shape cylindrical, the ends sym- 
metrically rounded; color dark brown; upper end covered 
by cap of excrement 3 mm in thickness ; below this, four or 
five closely related, thin, shining, light amber-colored mem- 
branes of a circular shape moderately interwoven with 
brown fibrils; below this, the domeshaped roof of the co- 
coon, dark amber-colored, more abundantly supplied with 
fibrils and presenting a dull finish internally; wall of co- 
coon composed of three layers from without inward as 
follows: (1) Thin dull brownish membrane closely ad- 
herent to clay wall of cell; (2) Thick dull brownish mem- 
brane; (3) Very thin, glistening, light amber-colored 
membrane sparsely supplied with interlacing fibrils. 
In the first paper, I remarked that there were large 
numbers of parasites flying about and entering the nests of 
Melissodes obliqua Say. The parasitic ratio of 30%, as 
shown by the incubation of the cocoons, tends to bear this 
out. However, in view of the fact that 29 of the 30 parasitic 
larvae failed to reach maturity (possibly due to my trans- 
ferring them from an incubator at 28° C. to room temper- 
ature) I have no doubt that there are other species of 
Triepeolus besides concavus, which are parasitic on this 
bee. It is such a set of mortality statistics which so often 
brings our experiments in the incubation of the larvse of 
wild bees to an unfortunate conclusion. 
Perdita opuntise Cockerell 
In my paper in Psyche, 1 concerning the nests of Perdita 
opuntise, it appears that there is room for some misunder- 
standing as to whether the bee actually nests in firm stone 
or makes use of various cracks and faults in which to con- 
struct its tunnelways. Mr. S. A. Rohwer, of the United 
States Department of Agriculture, in particular has called 
lr The Bee That Works in Stone; Perdita opuntice Ckll. Psyche, vol. 35, 
No. 2, pp. 67-84. (1928). 
