254 ENTOMOLOGICAL SOCIETY 
I may add that the sympathies of the numerous spectators were wholly 
on the side of the grasshopper. 
A PECULIAR HABIT OF CHALYBION CyERULEUM. This handsome steel- 
blue wasp of the family Sphecidce is quite common in summer and early fall 
in the parks and gardens of Washington. It stores its cells with spiders, 
but I do not know whether it selects only one particular species or 
several. At any rate, it seems to prefer a small, very common spider 
(? Dictyna}, which makes a loose and irregular web on hedges, windows, 
etc. The spider usually hides under a leaf, or twig, or projecting corner, 
and is rarely seen on the web itself. I have now noticed not only once, 
but repeatedly a pretty trick on the part of the wasp to secure its prey. 
It deliberately flies into the web of the spider, gets entangled, hangs 
down by its hind legs, flutters about; in short, acts like an insect that has 
been accidentally caught in the net. This last is, in many instances, not 
inhabited, and the wasp then disentangles itself without difficulty and 
flies away. If the net is inhabited the owner sallies forth from its hiding- 
place to look after the disturbance. Upon perceiving such a large insect 
in its web and possibly recognizing its deadly foe, the spider retreats as 
quickly as possible, but the wasp now knows where to look for it and 
easily captures it. 
During the discussion of predatory habits of different insects, 
Mr. Ashmead spoke of the peculiar habit of a Hymenopteron 
{Moncdula Carolina). It preys on the Horse-flies (Tabamis}. 
and often when driving he has seen this species keep ahead of the 
horse, flying backward all the time, and then make a dart and 
capture its prey from the horse's body. 
Mr. Townsend read the following : 
NOTES ON SOME INTERESTING FLIES FROM THE VICINITY OF WASH- 
INGTON, D. C. 
By TYLER TOWNSEND. 
The species which form the subject of these notes were collected dur- 
ing the past summer in the vicinity of the upper Potomac landings on the 
Virginia side of the river, and are rather striking flies, either from their 
appearance or their habits. 
Holcocephala abdominalis, Say. This is a queer-looking, spectacled- 
headed, predatory fly of somewhat inferior size, belonging to the family 
Asilidce, and sub-family Dasypogonince. The head is unusually broad in 
front, the eyes being very prominent and presenting a spectacled or 
goggled appearance. My specimens were taken from July 24 to August 
19, either on leaves of plants in rather low situations, or on the wing. 
They agree well with Say's description, though the abdominal segments 
seem to be darker above in some specimens than there indicated. To 
Say's description the following might be added : The coxae are entirely ashy ; 
