Mariana TrilloThe female spider Pisaura mirabilis prefers sperm from males that bring her a nuptial gift, like a meal. In another spider species (Paratrechalea ornata), females prefer the prey that males bring to be well-wrapped in silk, according to a study published in Naturwissenschaften last month (January 15).
Researchers from the Instituto de Investigaciones Biologicas Clemente Estable in Uruguay collected P. ornata spiders from the Santa Lucía River. They painted the mouthparts of some male spiders white to simulate carrying silk-wrapped prey and found that females touched and remained face-to-face with the painted males more than unpainted males. The team also tested whether male condition—starvation versus satiation—affected if and how thoroughly the male spiders wrapped prey. Male spiders in poorer condition did less wrapping; the prey in their gifts showed through the silk, appearing black rather than the white of the well-wrapped gifts from spiders in better condition. The researchers found that the majority of gifts collected from spiders in the wild looked white and were wrapped in more than one sheet of silk.
“Females evaluate the physical condition of a male based on his silk wrapping performance, and how the gifts he brings look,” coauthor Mariana Trillo said in a statement. In their paper, Trillo and her colleagues suggested that the white silk wrappings help these nocturnal spiders see nuptial gifts and that female spiders may use the color of the gift as an indicator of male condition and mate quality.