RUPTOR OVI, THE NUMBER OF MOULTS IN 
DEVELOPMENT, AND METHOD OF EXIT FROM 
MASONED NESTS. BIOLOGY OF 
EUMENINE WASPS, VII. 
By Kenneth \V. Cooper. 
Hanover, N. H. 
Many common mason wasps of the eumenine genera Ancistrocerus, 
Symmorphus , and Rygchium construct nests which, for a period from 
a month and a half to nearly ten months, must enclose and protect 
the food supply and the young wasps during their helpless egg, larval 
and pupal stages. These nests may be made by cross-partitioning into 
a succession of cells ready-formed, empty, blind tunnels, such as 
abandoned burrows of wood-boring insects, hollow stems of plants, 
or even holes left by large nails. Nearly each cell, as it is made, re- 
ceives an egg and sufficient paralysed prey (caterpillars or phyto- 
phagous beetle larvae, depending on the species of wasp) for 
development of a newly hatched larva to the adult wasp. The pro- 
tective plug that closes the completed nest, and the partitions between 
cells, are made by the female wasp from a cohesive mortar of clay, 
loam or sand, worked up with water (and perhaps “saliva”). Other 
wasps of these genera, and of more or less related genera such as 
Eumenes and Psmdo/nasaris (a masarine), fashion their entire nests 
of mortar, building aggregates of masonry tubes, pots, or lumpy 
masses of cells affixed to plant stems, bark, or the exposed faces of 
rocks. Not only must the nests of mason wasps be hard and suffi- 
ciently strong to resist possible mechanical stresses and penetration by 
parasites but, being often subject to rain and melting snow, like man’s 
masonry, they must withstand dissolution when built in exposed situ- 
tions. 
It is not surprising that the walls and plugs of such nests serve 
other functions than mere protection. For example, they prevent 
cannibalism among the brood, they serve hygienic functions, they 
make possible the use of lightly paralysed prey, and so on. They also 
serve as the channel of an essential communication system between 
mother and young that their very presence necessitates; these and 
other matters I have discussed elsewhere (Cooper 1957 )- But if 
the cement- or plaster-like masonry succeeds in keeping other insects 
out of the nest, as in general it does so well, by what means do the 
developed wasps, imprisoned within the nest, gain their exit? 
Manuscript received, by the editor December 5, 1966 
