121 
to the inclemencies of the weather. The nest is a heavy mass of 
clay streaked with little ridges and enclosing several cells. At 
first the cells, which are built parallel to one another. have only 
medium-thick walls (Fig. 58); when their number is complete, 
however (usually three to five), their exposed surfaces are cov- 
ered by additional mud, with the final effect as shown in Bigs 7. 
A cross-section of such a nest will show vault-like cells—their 
inner walls only 1 or 2 mm. thick, their outer 5 mm. or more. | 
opened several nests; some of the cells had been appropriated by 
a colony of Crematogaster ants, while others contained or had 
contained parasites—in one case a 
brilhant green cuckoo wasp, in 
another 20 muscoid fly puparia. 
Another nest had part of its cells 
occupied by a pompilid wasp, Pseu- 
dagenia, that had subdivided the 
large cell to suit her needs. Several 
of these wasps were reared. An- 
other cell of this nest was used by 
a leaf-cutter bee (Megachile) as a 
home for her brood, while © still 

Fig. 58a. Cross-section of a 
completed nest of S. in- another contained some decayed 
trudens, to show the thick lepidopterous larvae, indication that 
outer walls. Reduced. the eumenid wasp Rhygchium had 
come in for her share of cell 
space. Thus three species of Hymenoptera had made use of 
this nest, and such a circumstance recalls my reading somewhere 
of annoying mistakes made by observers in giving a wasp the 
credit for building a nest which is really the work of another 
species. 
This big mud-dauber stores her cells with a variety of spiders, 
some of goodly size, and on one of which, in each cell, she lays 
an egg; this is somewhat curved, 4 mm. long by about 0.9 wide. 
It is placed on the underside of the abdomen of a quiescent 
spider. The grub which hatches feeds at first immovably, suck- 
ing its victim’s juices; later on it transforms into the biting 
stage, when it consumes the spiders by chewing them up. When 
full-fed it measures about 26 mm. long, 1s rather slender and of 
a pale dirty brownish yellow color. In spinning it first makes a 
weak scaffolding of silken threads and then forms the typical 
thin, blunt cigar-shaped cocoon, in this case quite dark in color 
(lies 57) 
Some of the completed nests are two-thirds as large as a 
tennis ball; the wasp often spends many days in adding to- the 
