3§ 
The Ohio Naturalist. 
[Vol. VII, No. 2, 
NOTE ON HABITS OF SENOTAINIA RUBRIVENTRIS MACQ * 
Herbert Osborn. 
This species of tachinid has been observed on several different 
occasions at Cedar Point, and its habits are of such interest that 
the record of some of these observations may be in place. In 
the vicinity of the laboratory certain pompilid wasps are quite 
common and may very frequently be seen dragging spiders with 
which to provision their nests. On several occasions during 
the summers of 1905 and 1906, I have observed these tachinid 
flies following the wasp as it drags its burden along the sand. 
The flies may vary in number from two to as many as nine, the 
highest number noticed, and in following the wasps hover at a 
very constant distance, about six or seven inches, progressing 
and halting almost mechanically with the movement of the 
spider. If the spider is dropped, the flies remain stationary, 
hovering an inch or two above the surface of the sand or, if the 
spider is left for some minutes, they may’ rest upon the sand, but 
alway r s with the head directed toward the spider, and apparently 
with the attention concentrated fixedly upon it. So intent are they 
upon this object that they may be pushed about with a stick or 
otherwise interfered with, with scarcely^ any diversion from their 
intentness. Immediately upon the return of the wasp and move¬ 
ment of the spider ,they are on the wing and maintaining the 
constant distance noted. The wasp appears to pay but little 
attention to them, although if approached too closely, it may 
show some slight indication of annoyance and the flies appear to 
be on the alert for any offensive action on the part of the wasp. 
On one occasion I had the opportunity to see the actual en¬ 
trance of the flies into the burrow. The flies hovered at about 
the usual distance from the spider while it was resting at the 
mouth of the burrow, but appeared unusually excited, making 
quick movements sidewise in maintaining attention upon the 
spider and when finally the spider was dragged into the burrow 
a very quick movement was made and some of the flies were seen 
to actually pass down in the burrow but apparently only one 
or two succeeded in entering and remaining; perhaps the one 
first getting opportunity to enter being recognized as the rightful 
inhabitant. Clearly the entrance of the burrow was for the pur¬ 
pose of depositing eggs and we cannot doubt that the' species, 
is parasitic within the nest of this pompilid. A related species, 
Senotainia trilineata, is recorded as being reared from the nest 
of Sphecius speciosa. The species was kindly determined for me 
by Prof. J. S. Hine. 
Read at the meeting of the Ohio S1a‘e Acad, of Science. 
