1934 ] 
Entomological Investigations in Panama 
173 
throughout the day and until late in the evening, seeming 
to become more active at twilight. They were vicious biters 
and very persistent in their attempts to obtain blood. They 
apparently were attracted by motion and when one was 
moving in the forest they followed to circle about with a 
vicious hum and dart at one’s face, hands or any exposed 
part of the body and immediately begin biting. If one 
stood or sat quietly for a few minutes most of these flies 
gradually disappeared, although a few invariably remained 
and continued their efforts to feed. They were to be found 
by the hundreds attacking the mule at nearly all times. 
Some preference seemed to be shown for the neck and head 
but they were found on nearly all parts of the animal’s body 
at times. They were rather slow in filling with blood and 
when gorged became quite sluggish. The wings were held 
partly extended while feeding. Although this species was 
much more common along the edge of the forest, they fre- 
quently appeared in bright sunlight as well. 
Dichelacera submarginata Lutz. This was nearly as 
abundant as D. analis and 94 specimens were collected, fif- 
teen found inside the camp resting on the screens. They 
seemed to center their attacks upon the mule and appar- 
ently were not much attracted by humans, only one being 
taken while biting man. They attacked the mule all during 
the day and early evening and, strangely enough, never at- 
tempted to feed on any part of the animal except the lower 
legs. From 20 to 50 were usually present on each leg and 
it was very seldom that a single individual was noticed bit- 
ing above the knees. They gathered in masses at the fet- 
locks and around the coronary region at the top of the 
hoofs. They are slow feeders and required some little time 
to engorge. The mule did not seem to experience much an- 
noyance from their attacks and seldom stamped its feet to 
prevent their bites. When brushed from the animal’s legs 
these flies flew only a few inches and immediately returned 
to resume their feeding. They seemed to be noiseless in 
flight when approaching or leaving the mule. 
Tabanus albocir cuius Hine. Flies of this species were 
