110 
which build their nests in nearby trees or sheds close to their foraging 
ground. The prickly branches of the osage orange trees, which often 
grow along the roadsides, are favorite locations for them. 
It is difficult to estimate the amount of good done b}^ the wasps, 
but there can be no doubt that it is ver}^ considerable, probably exceed- 
ing that done by an}^ other of the predaceous enemies. They are at 
work from daylight until dark, constantl}^ in search of larvae, and the 
vast numbers foraging in the cotton fields must necessarily destroy 
the bollworm almost exclusively. The most abundant and undoubt- 
edly the most beneficial form is Polistes anmdaris. 
On one occasion a nest of P. annularis at Pittsburg, Tex., was 
watched by Mr. Bishopp to ascertain the number of bollworms brought 
in b}" the wasps. The nest was of medium size, consisting of about 
twenty-five or thirty cells, with pupae, 200 to 250 larvae, and 30 adults 
present at one time on the nest. During a period of half an hour eight 
bollworms and one Geometrid caterpillar were brought in by the 
wasps and fed to their larvae and to other adults. 
From these facts it is apparent that the present custom of wantonly 
destroying the nests of these wasps where they occur in or about cot- 
ton fields is a bad practice and should be disparaged strongly, so that 
the wasps may have full swaj" in their beneficial work. 
The wasps also frequent corn fields, and we have often watched 
them searching for bollworms w^here we have passed along the rows 
stripping the shucks from the ears and removing the larvae. Several 
times they were seen to pounce upon larvae left intentionally upon the 
ears. In cotton fields, where the larvae are most exposed, the wasps 
are continually in search for them, feeding by turns on the honey 
secreted by the nectaries on the squares. 
Forming another group of predaceous enemies are a few large species 
of robber flies (Asilidae) which frequent the fields. These flies do not 
destroy the larvae, but confine their attacks solely to the moths. The 
only species actually seen with a bollworm moth was the large brown . 
Deromyia angustipennis Loew, but judging from their observed habits 
the numerous Erax and Mallophora (PI. XVIII, figs. 3 and tt) must 
undoubtedh^ catch the moths also. On one occasion a specimen of 
Deromyia was brought into the laboratory and tested as to its feeding- 
habits. A bollworm moth was introduced into the jar with the fl}-, 
and although the latter was much hampered by lack of freedom, 
scarcely two seconds elapsed before it had secured the fluttering moth 
firml}^ between its legs and was inserting its sword-like proboscis into 
the moth's hodij. The following is a list of the more common robber 
flies which were observed in the cotton fields: 
Erax lateralis Macq. Deromyia umbrinus Loew. 
Erax bastardii Macq. Dizonias bicinctus Loew. 
Mallophora orcina Wied. Sderopogon latipennis Loew, 
Deromyia angustipennis Loew. 
