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Psyche 5:404, 1888.

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404 PSYCHE. [August--October 1890.
SPIDERS.-In the spring of 1887 while hunt- ing for spiders in company with Mr. G.
Dimmock in the cracks on the steep sides of some ~-ocks near Roberts Station in Wal- tham, Mass. I found hanging in cobwebs
several soft white maggots and pupae.
The
webs were generally old and out of repair and a closer examination showed that there were no living spiders in them but in almost
every one an empty skin of a common
spider, Amaarobius sylvesfris, nearly full grown. The skin of the legs and thorax was not clean like a moulted skin but dirty
and opaque as though eaten out and the
skin of the abdomen when present was torn and shrivelled. "From this I concluded that the maggots came out of the spider and
from their size must have nearly filled them. The maggots varied considerably in size the largestbeing a quarter of an inch long while others were not much more than half as
large. The hinder half of the body was
thicker than the front half and nearly spheri- cal.
They hung head dpward holding to the
web by their jaws and were also partly sup- ported by threads under and around them. I was unable that season to raise the adult fly some of the larvae being injured in carrying them home though kept in cobwebs and
cotton wool and the others dying apparently fropi too dry air w'thin a few days. In May 1389, I again found in the same locality several other specimens also in abandoned cobwebs and with the dead and empty
spiders as before and among them one pupa ,
far enough advanced to grow to the adult condition though the skin dried so much
that it had to be torn oft'and the fly never expanded its wings properly. It turned out to be a species of Acrorera belonging to a family several species of which. have been found parasitic in the same way in spiders. In his monograph of the spiders of Prussia (Schriften der Nat. Gessel. Danzig 1863-1866) Menge mentions a similar case. He kept in the house a female Chibiona fut& in its
nest attached to a heath plant. After a
few days the spider died and shrivelled
and in its place was a maggot suspended
by a thin web across the nest. Next day it pupated and a week later there came out the fly, Heiio$s marg-iizatm Meigen.
F. Brauer (Verb. d. 2001-bot.-gessel.
Wien, 1869, p. 737) describes Astomella
findeaii Er., which came from Cteniza
iiriana Koch, a trap-door spider from Corfu. The pupa and larva skins were found in
the tube and also the dead spider with
the abdomen shrunken and having in front a large hole from which the maggots had
escaped.
Both these flies belong to the acroceridae. My specimen has been examined by S. W.
Williston who thinks it is either Acrocera faviata or a species closely related to it. J. H. E?ne~,ton.




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