1929] 
Melissodes obliqua and Perdita opuntiae 
293 
NOTES ON COCOONS AND PARASITES OF MELIS- 
SODES OBLIQUA AND NESTS OF PERDITA 
OPUNTIAE (HYMENOPTERA-APOIDEA) 
By Clarence P. Custer 
Melissodes obliqua Say 
I have recently described the nests of Melissodes obliqua 
Say in The Canadian Entomologist. 1 Since then I have bred 
102 cocoons, obtained from the nests of the species, with the 
following results: 
Of the 102 cocoons, 72 contained larvae of the host and 
30, those of the parasites, revealing a parasitic ratio of 
approximately 30%, — or about one parasite to every two 
hosts. Of the 72 hosts, 48 were male and 24 were females, 
the males reaching maturity somewhat earlier and in larger 
numbers than the females. This gives a sex ratio of two to 
one in favor of the males. Of the thirty parasites, all died 
except one, Triepeolus concavus Cresson, which reached 
maturity after 10 months incubation (August to June). 
Since there is no fundamental difference between the 
cocoon containing the host and that containing the parasite, 
one can conclude that this Triepeoline Bee is carnivorous. 2 
For in order to develop in the cocoon of the host the 
parasite must have postponed its feast until the pollen and 
honey were consumed and the cocoon spun. It is interesting 
to note that the parasitic larvae possess two rows of dorsal 
iOn the Nesting Habits of Melissodes Latr. (Hymenop.). Canadian 
Entom., vol. 60, p. 28, 2 figs. (1928). 
2 Reinhard, in a recent publication on wasps, states that the cocoon of the 
parasite, Nysson hoplisivora, is indistinguishable from that of its host, Hoplisus 
costalis, except for its slightly smaller size. If his observations are correct, my 
conclusions must be regarded with reservations. Only time can reveal the 
answer. The problems of parasitism have, to say the least, wide fields for 
future study. 
