10 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62, 
in arid regions and on sand dunes where there is little or no vege- 
tation. 
The writer had the opportunity of observing the imagines of Diali- 
neura crassicornis in the Hood River Valley of Oregon and in the 
vicinity of Stanford University, California. This species is found on 
rocks and sand along stream beds where the country is open and 
sunny. In the vicinity of Stanford the adult flies were first noticed 
on April 27 in 1920, all the specimens observed on that date being 
males; these males were very alert and would not allow a near ap- 
proach until they became accustomed to one’s presence. They would 
stand on the rocks and sand with the front legs almost straight, the 
front end of the body thus being tipped up. Now and then one would 
fly up suddenly some 5 or 10 feet in the air and two or three others 
would start in pursuit. They were evidently awaiting the appearance 
of a female and would fly up after small pebbles tossed in the air near 
them, reaching the pebble before it started to fall and pursuing it to 
the ground in many instances. They would continue this game as 
long as one cared to throw for them and seemed to catch sight of 
the object some 10 feet away. Perhaps the larger facets on the 
upper part of the eye of the male permit an unusual vision. On a 
near approach to the object thrown in the air the flies would sense 
their mistake and return to the ground. None of them were seen 
feeding on other insects. The females were observed about a week 
later than the males and were much less active, none of them paying 
any attention to objects thrown near them, or to other insects flying 
over, as in the case of the males. Most specimens kept in captivity 
lived only two or three days, but two females, fed on sugar water, 
lived about eight days. 
Adults of Thereva vialis were observed in the same localities with 
D. crassicornis and their habits were much the same. They appeared 
to emerge a little later and had alongerseason. They lived no longer 
in captivity than the other species and no eggs were obtained from 
either. 
EARLY STAGXS OF THE THEREVIDAE. 
Very little is known of the early stages of these flies or their habits, 
nothing being known of the egg stages. Zetterstedt, in a paper pub- 
lished many years ago, recorded one species of Thereva ovipositing 
insand. The older larvae of several species are known and have been 
found to have various habits. They have been found in earth and 
decaying wood, feeding upon decaying vegetable or animal matter. 
Some specimens have been found singly under moss, fir needles, cow 
dung, fungus, decaying wood, especially alder branches. The larvae 
are predaceous and even cannibalistic. Westwood found Thereva 
larvae in pupae of Aleucis pictaria and Sphinz ligastri and the larvae 
