80 Psyche [March-June 
bowed and the width is one-half the height; the femoral setae are 
lacking, the hind tibiae have but a single seta, and the coxal hairs 
are shorter. 
Chersodromia megacetes, n. sp. 
Length 2 mm. Body black, thinly coated with cinereous 
pollen except the following polished places: face, proboscis, a 
narrow vertical stripe on sides of lower occiput, mesonotum 
except a narrow margin on sides and rear, most of sternopleura, 
terminal plate of pygidium and side of front coxae. Palpi yel- 
lowish. Mesonotal hairs abundant, dark, leaving two approxi- 
mated glabrous stripes anteriorly, separated by the biseriate 
hairs of the median line; scutellum thinly cinereous, two apical 
scutellars. Last tergite of abdomen of male somewhat enlarged 
on the left side; pygidium enormous, massive, twisted to the 
right, ventral bowl nearly twice as long as wide, below and 
laterally on the right side with a few short hairs, left side above 
with a shining spatulate valve, terminal disk rounded triangu- 
lar; last segment of female abdomen compressed and shining, 
as long as other single segments. Legs black, the knees, extrem- 
ities of tibiae and the tarsi fuscous; femora without bristles 
other than a small one near knee, hind tibiae with a few small 
bristles on apical half and inwardly with a terminal lappet, 
middle tibiae with a flexar comb of short setulae. Wings and 
veins whitish, the costal bristle black but the minute hairs 
whitish, crossveins touching, or the posterior crossvein slightly 
before the anterior; halteres wholly white. 
Type, allotype and seven paratypes: Corona del Mar, Cali- 
fornia, 28 December 1944. Seven additional paratypes from 
the same locality, 25 July 1942, from Laguna Beach, 25 Janu- 
ary 1935 and 22 May 1944, and from San Clemente Beach, 23 
May 1944. In all, five males and eleven females were taken. 
The insects occur on the dry sand above the line of washed-in 
seaweed. They are reluctant to fly, can be driven into the col- 
lecting net, and are prone to take refuge in the burrows of 
Amphipods. 
The species name, while literally meaning a great whale, has 
been applied to anything excessively large. In the present in- 
stance the monstrous pygidium, bulking as much as the re- 
mainder of the abdomen, and relatively larger than possessed 
by any other fly, warrants even this hyperbolic appellation. 
