Web vibrations in intraspecific contests of female black widow spiders, Latrodectus hesperus

Authors: Krugner, Rodrigo; Espindola, Crystal; JUSTUS, NATHAN - Oregon State University; HATTON, ROSS - Oregon State University

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2022
Publication Date: 2/2/2023
Citation: Krugner, R., Espindola, C., Justus, N., Hatton, R.L. 2023. Web vibrations in intraspecific contests of female black widow spiders, Latrodectus hesperus. Environmental Entomology. 52(2):169-174. https://doi.org/10.1093/ee/nvad003.
DOI: https://doi.org/10.1093/ee/nvad003

Interpretive Summary: Female black widow spiders, Latrodectus hesperus Chamberlin and Ivie, are solitary predators of arthropods with no tolerance for intruders on their webs. In California, L. hesperus can be a phytosanitary pest in crops destined for domestic and international markets. Spatial separation of L. hesperus webs could be determined by natural territorial rivalry between females, but little is known about female-female communication behaviors in this species. In laboratory observations, displays of female-female rivalry included emission of vibrational signals, with the number of signals emitted by both females being highest during the beginning of the observations. The overall ratio of signals emitted by the resident and introduced females was about 4:1, with the number of signals emitted by resident female higher than the number of signals emitted by the introduced female. Collectively, these results demonstrate that female L. hesperus exhibit territorial rivalry and that female-female rivalry is mediated by emission of vibrational signals through the web. Understanding the mechanisms of intraspecific competition in L. hesperus may lead to development of novel methods to prevent spiders from colonizing crops.

Technical Abstract: Female black widow spiders, Latrodectus hesperus Chamberlin and Ivie, are solitary predators of arthropods with no tolerance for intruders on the webs. In California, L. hesperus are found in urban and agricultural settings and can be a phytosanitary pest in crops destined for domestic and international markets. Spatial separation of L. hesperus webs could be determined by natural territorial rivalry between females, but little is known about female-female communication behaviors in this species. In 1-hour laboratory observations, displays of female-female rivalry included emission of vibrational signals in a majority (20 of 30) of trials. The number of signals emitted by both females was highest during the initial 10 min of trials, with signaling rate (time interval between signals) peaking during the 40-50 min observation period. The overall ratio of signals emitted by the resident and introduced females was about 4:1, with the number of signals emitted by resident female higher than the number of signals emitted by the introduced female. Analysis of rivalry signals showed a peak in magnitude (about 0.4 m/s) ranging from 6 to 23 Hz and smaller peaks at about 29, 38, and 47 Hz. Collectively, these results demonstrate that female L. hesperus exhibit territorial rivalry and that female-female rivalry is mediated by emission of vibrational signals through the web. Understanding the mechanisms of intraspecific competition in L. hesperus may lead to development of novel methods to prevent spiders from colonizing crops.