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Although many characteristics of the egg sacs of spiders likely evolved to reduce the effect of parasites and predators that attack their eggs, many parasite and predator insects have become specialized on spider eggs. Eggs of six of the seven species of Theridiidae included in this study were attacked by wasp parasites (Baeus achaearaneus, Idris sp., and Comastichus zopheros), and two by the specialized spider egg predator (Neuroptera: Zeugomantispa minuta). The incidence of parasites in the egg sacs varied across species. Parasites attacked more than 60% of the egg sacs of Tidarren sisyphoides and Parasteatoda tepidanorum, but none of the sacs of Latrodectus geometricus. The incidence of parasites in the egg sacs was higher during the dry season for T. sisyphoides, and during the rainy season for P. tepidanorum. The proportion of the eggs parasitized per egg sac varied from 0.09 (± 0.19) in Nesticodes rufipes to 0.50 (±0.46) in T. sisyphoides. Differences in the biology of parasites, as well as in the structure of spider webs and habitat preference of spiders, may influence the incidence of parasitism and proportion of eggs parasitized in each egg sac.
A fossil pirate spider (Araneae, Mimetidae) is documented in amber from the Eocene Cambay Formation of India. It represents the first described spider from this deposit and the oldest fossil record of the family, extending its known geological range by approximately 3–8 million years from the previously oldest fossils in Eocene Baltic amber. It also represents the first Gondwanan geological locality for fossil mimetids. Despite the application of X-ray computed tomography to the study of this inclusion, the state of preservation of the juvenile spider did not permit identification beyond family level.
The Arachnida and Myriapoda collections at the Natural History Museum are of world-class importance. They comprise over 30,000 jars of spirit, as well as more than 74,000 microscope slides, 180 drawers of dry, pinned specimens, and 40 drawers of spiders egg sacs and nests. Approximately 21,270 species are represented, although this estimate is below the number actually present. The purpose of this paper is to give a brief overview of the early history of the Arachnida and Myriapoda collection, to provide historical information of specific interest to researchers, to discuss the history of the section from 1990 to the present, and to detail all data sources available that relate to the collections, such as accessions registers, collections indexes, card indexes, reprints, databases, and archives. It is hoped that the information contained will provide a useful resource to potential researchers.
The holotype and only known specimen of Juraraneus rasnitsyniEskov, 1984, the first spider to be described from Jurassic strata, is redescribed and re-illustrated using modern photographic techniques. Juraraneus is shown to be a cribellate araneoid, and thus forms part of the cribellate stem-group orbweavers which pre-dated the ecribellate araneoids found today.