Published data
on egg sizes and egg numbers in Pholcidae have been mostly anecdotal,
like in other spider families. Here we attempt a comprehensive
compilation of egg size and clutch size data in pholcid spiders. Three
aspects combine to make pholcid spiders an ideal group for such a
compilation of data. First, pholcid egg-sacs are usually ‘covered’ by a
few turns of silk only, allowing precise egg measurements without
manipulating the egg-sacs. This is in contrast to many other spider
families where a dense layer of silk impedes a direct view of the eggs.
Second, pholcids carry their egg-sacs with their chelicerae. As a
result, a photo showing a female with her egg-sac combines data on body
size, egg size, and egg number. And third, my database (partly
accessible here) contains
thousands of photos showing females with egg-sacs. Females (and in many
cases egg-sacs) originating from the same localities as the
photographed females are available in all cases, allowing a
transformation of screen (photo) measurements to real values.
We found the expected strong effects of female body size and egg size
and number, but also some unexpected effects such as an effect of body
shape. Here some examples. Dark points and line symbolize species with
long abdomen, light grey points species with short abdomen.
Some female pholcids and their egg sacs. A. Belisana
sp. (“Mal3”), Singapore. B.
Calapnita nunezae,
Philippines. C. Carapoia alagoas, Brazil. D. Carapoia
agilis, Brazil. E. Mecolaesthus cornutus, Venezuela. F. Litoporus
curimagua, Venezuela. G.
Ninetis(?) sp. (“Om84”),
Oman. H. Metagonia reederi, Galapagos. I. Guaranita goloboffi (ventral view),
Argentina. J. Metagonia latigo, Venezuela. K. Uthina
luzonica, Malaysia.
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