Growth, development, and survival in the brown widow spider, Latrodectus geometricus, under different feeding regimes
Abstract
Adult female spiders of the brown widow spider, Latrodectus geometricus CL Koch, 1841, lay multiple egg sacs during their lifetime, with each egg sac containing between 50 and 250 offspring. The mother supplements her developing embryos with additional lipids and proteins, and the spiderlings undergo one molt within the egg sac before emerging. Thereafter, the spiderlings may remain in the mother's web for up to several days, and then disperse and build their own webs and seek prey. Prey availability, however, is unpredictable, and may differ among habitats. For synanthropic spiders like L. geometricus, that live in close proximity with human dwellings, prey availability might vary considerably. Here, we compared mortality, growth and development of the brown widow spider, Latrodectus geometricus, from neonate to adult under two different prey availability regimes. Growth curves were plotted by weighing spiderlings fed weekly or every three weeks on fruit flies and then blow flies or crickets. Mortality rates were significantly higher when spiderlings received less prey, and only 7 spiderlings survived when fed intermittently, whereas of those fed weekly, approximately 60% reached adulthood. Males developed linearly, molted a mean of approximately 4 times, and attained maximum body masses after ∼100 days, whereas females developed exponentially, molted 8-9 times, and reached maximum body masses after ∼170 days. The growth rate of males was consistent across different instars whereas it was highest in later female instars. Mature males were less than 1% as large as mature females, revealing extreme sexual size dimorphism in this species.
Jeffrey A. Harvey, Francesco Gerosa, Rieta Gols, Wilco C.E.P. Verberk "Growth, development, and survival in the brown widow spider, Latrodectus geometricus, under different feeding regimes," The Journal of Arachnology, 53(3), 154-161, (2 January 2026) https://doi.org/10.1636/JoA-S-24-013
