ART, 4. REVISION OF THE FAMILY THEREVIDAE—COLE. am 
of Psilocephala eximiain Noctua. Bergenstamm found the larvae in 
decaying oak wood in which the larvae of Adelocera lived. 
Collinge has described the early stages of Thereva nobilitata from 
England ‘and expresses the opinion that all of the species have more 
or less economic importance in the larval state. The larvae move 
like an eel or snake, not being able to draw themselves together as 
most other dipterous larva do. Collinge noted that the larvae pre- 
ferred compact but sandy soils, making use of earthworm burrows 
when in wet soil and forming small side chambers along them. He 
found larvae at the roots of currant trees and some at the roots of 
pinks and violets. These larvae were fed on the larvae of Ceutor- 
rhynchus sulcicollis, also on fly larvae and small earthworms. The 
upae were found on the surface of the soil or only partially covered 
ry; it. 
Hyslop described the larva and pupa of Thereva egressa Coquillett 
and the feeding habits* from observations taken at Pullman, Wash- 
ington. ‘The larva was found in a wheat field in May, and when 
taken it had its head and first four anterior segments inside of an 
elaterid larva and was feeding on the viscera. The larva was fed on 
one or two elaterid larvae every day until June 10, when it pupated. 
From the description the larva is the typical of the family. The 
length at first was 25 mm. and 30 mm. just before pupating, with 
the thoracic segments much swollen. The pupa is evidently much 
like some of those in the genus Psilocephala, the length being given 
as 15mm. The pupal stage in this case lasted 14 days. 
Hyslop also reared Psilocephala aldrichi Coquillett and P. munda 
Coquillett from larvae taken in the field, associated with elaterid 
larvae and probably predaceous on them. 
DESCRIPTIONS OF THE LARVAE AND PUPAE. 
The larvae of the Therevidae are quite long and slender, cylindrical, 
chitinized, tapering at the two ends; the head small, heavily chiti- 
nized, and darker in color than the rest of the body; the mandibles 
well developed and pointed apically; antennae quite small. The 
prothoracic spiracle is distinct and there is a bristlelike hair on the side 
of each thoracic segment near the middle. The abdominal segments 
1 to 6 are divided by constrictions so that there appear to be 20 
segments in all. The anterior spiracles are on the segment behind 
the head, the posterior spiracles on the antepenultimate segment; 
the last segment ends in two short fingerlike processes. 
The pupae are distinguished from those of the Asilidae by the 
presence of two horns (antennal sheaths) on the head, pointing out- 
ward, and a tubercle with a curved spine near the base of each wing 
4Journ. Econ. Biol., vol. 4, pp. 14-19. 
5 Proc. Ent. Soc. Wash., vol. 12, p. 98, 1910. 
