Micropholcus in Dominican Amber - and a first case of egg parasitism in Pholcidae
Published in Journal of Natural History, 2006; http://dx.doi.org/10.1111/j.1463-6409.2006.00239.x; PDF
In 2004 I received in loan this magnificent piece of Dominican amber from Jörg Wunderlich. The spider inside is the first representative known of the genus Micropholcus in amber, dating back about 23 million years. I tried to find more specimens in amber during a trip to the Dominican Republic, without success. What I did find were several new species of extant Micropholcus species, and these are described, together with the fossil species, in this paper.

Another highlight of the trip to the Dominican Republic was the discovery of the first case of egg parasitism in Pholcidae. Females in Pholcidae carry their egg-sacs in their chelicerae until the spiderlings hatch and it is probably for this reason that the eggs are not densely covered by a protective layer of silk as in most other spiders.

It seems that very few egg parasites have managed to access these protected eggs of Pholcidae. Baeus wasps (photos below) are specialized to burrow through dense silk covers of other spider eggsacs. On Hispaniola they have discovered that they can lay their eggs on pholcid eggs and have their offspring protected by the mother whose offspring they are killing!

Left: unparasitized and parasitized eggsacs of Micropholcus baoruco
Below: Baeus sp. female from one of the parasitized pholcid eggs. Scale bars: 0.2 mm.