Summary: © The Norwegian Academy of Science and Letters 2005 · Zoologica Scripta, 34, 4, July 2005, pp389413 389
Agnarsson, I. (2005). Revision and phylogenetic analysis of American ethicus and rupununi
groups of Anelosimus (Araneae, Theridiidae). -- Zoologica Scripta, 34, 389413.
Two species groups of the social spider genus Anelosimus are revised. The ethicus group
contains six species found in South America, in an area ranging from the Guianas to southern
Brazil and Argentina. Of these, A. rabus Levi, 1963, A. ethicus (Keyserling, 1884), and A. nigrescens
(Keyserling, 1884) are redescribed, while A. nigrescens is removed from synonymy with A. ethicus.
Three new species are described: A. misiones sp. nov., A. sumisolena sp. nov. and A. inhandava
sp. nov. Anelosimus ethicus is reportedly either subsocial or solitary, while the behaviour of the
other species in the group is unknown. The rupununi group contains two quasisocial species,
A. rupununi Levi, 1956 and A. lorenzo Fowler & Levi, 1979, from the Caribbean and tropical
South America. Both are redescribed here. A parsimony analysis of morphological characters
provides support for the monophyly of both groups. In the phylogeny, subsociality optimizes
to the base of Anelosimus, indicating that the common ancestor of the ethicus group was sub-
social. Its members can thus be predicted to be subsocial, or secondarily solitary. Quasisociality
arose de novo in the rupununi group, representing one of 6-7 independent origins in theridiids.
Study of the biology of Anelosimus is important to advance our understanding of the evolution
of sociality in spiders.
Ingi Agnarsson, Systematic Biology -- Entomology, E-530, Smithsonian Institution, NHB-105, PO
Box 37012, Washington, D.C. 20013-7012, USA & Department of Biological Sciences, George