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against? No doubt the large solitary hornet (Vespa deusta), 
a very destructive creature, may sometimes try to gain entrance 
into the open cell. Ants frequently swarm on bushes and must 
be considered a menace. The ubiquitous eumenid wasp Ihyg- 
chium appropriates the cells of old nests and would not be so 
harmless if given free access to an occupied nest. But per- 
haps the most successful foe of our wasp is a large chalcid wasp, 
Leucospis, a cosmopolitan genus of mostly black and yellow 
species which have the peculiarity of longitudinally folded wings. 
This insidious creature has been found by Fabre to parasitize 
the cells of Chalicodoma and Anthidium, both solitary bees. No 
doubt it preys upon many other species of solitary bees and 
wasps. Apparently Leucospis does not enter the cells of Zethus, 
but hangs around for days and at an opportune time thrusts 
her long ovipositor to the base, through the leafy layers, 
and may thus reach the young wasp within. Sometimes the 
watchful proprietress perceives the pest and routs it by a short 
dash; on other occasions, however, the parasite works in safety, 
hidden behind the bulk of the nest, the poor mother wasp stand- 
ing guard at the entrance to the cell. 
One finds many incomplete nests, usually full of ants. The 
rutelid beetle Adoretus sometimes uses deserted nests during the 
day as a retreat, crawling in among the leaf layers, and a small 
moth caterpillar spins up and feeds on the leaf-bits. 
This gifted wasp is to be found throughout the year, and while 
not abundant was more frequently taken during the rainy sea- 
son. It seems to have a special fondness for the umbellate 
flower heads of Premna odorata, a small wide-spreading tree of 
the Verbena family. 
The wasps of ne genus Synagris, though not very closely re- 
lated to Zethus, Hee some habits in common with tt. According 
to Roubaud (1910), who studied this genus in Africa, the ee 
specialized kinds of Synagris carry on their nesting activities 
much as in Odynerus and Eumenes, storing the cells with cater- 
pillars and then closing them. But more highly-developed forms, 
although they also make mud cells, feed hei young from time 
to time and guard the nest just as in Zethus. S. cornuta goes 
further still, in that she feeds her young, not with a somewhat 
chewed-up caterpillar, but with one worked into a mass. The 
cells, although of mud, have the narrowed and bent neck and 
enlarged bottom of the leaf-bit cells of Zethus. 
Zethus seems to differ in structure from some of the Amer- 
ican forms and appears restricted to the Old World tropics. 
Some of the American species of Zethus build mud nests. 
