"Hi, I'm a crepuscular spider, want to mate?" Doesn't sound too enticing, does it? That's probably why male crepuscular spiders (crepuscular means "active at twilight") need to grease the wheels with a few gifts. However, any old gifts won't do: in this study, the researchers show that female crepuscular spiders prefer silk-wrapped gifts, and they will mate more with males offering these tokens. Because silk takes energy to produce, these gifts actually serve as an indication of the health of the male. But really, who doesn't like to open a gift? "A partially-eaten beetle? Aw, you shouldn't have."
"An extensive diversity of nuptial gifts is known in invertebrates, but prey wrapped in silk is a unique type of gift present in few insects and spiders. Females from spider species prefer males offering a gift accepting more and longer matings than when males offered no gift. Silk wrapping of the gift is not essential to obtain a mating, but appears to increase the chance of a mating evidencing a particularly intriguing function of this trait. Consequently, as other secondary sexual traits, silk wrapping may be an important trait under sexual selection, if it is used by females as a signal providing information on male quality. We aimed to understand whether the white color of wrapped gifts is used as visual signal during courtship in the spider Paratrechalea ornata. We studied if a patch of white paint on the males' chelicerae is attractive to females by exposing females to males: with their chelicerae painted white; without paint; and with the sternum painted white (paint control). Females contacted males with white chelicerae more often and those males obtained higher mating success than other males. Thereafter, we explored whether silk wrapping is a condition-dependent trait and drives female visual attraction. We exposed good and poor condition males, carrying a prey, to the female silk. Males in poor condition added less silk to the prey than males in good condition, indicating that gift wrapping is an indicator of male quality and may be used by females to acquire information of the potential mate."
Bonus excerpt from the full text:
"To study if white color attracts female and affects male mating success, we presented virgin females with males in three experimental treatments. Males that had the front of their chelicerae painted white (n = 21); males that were not painted (n = 22); and males that had the sternum (ventral cephalothorax) painted white (n = 20), not visible by females and as a control of any paint effect (Fig. 1). We exposed females to males without a gift in order to avoid any chemical or behavioral factor not related to color affecting male and female behaviors, such as substances associated with gift silk (Brum et al. 2012) or male manipulation of the gift. All painted males were treated with white acrylic paint (Liky), at least 2 days before the trial. For painting, we immobilized males between two kitchen sponges and left their chelicerae uncovered; afterwards we painted them using a tiny paintbrush. Immediately after the manipulation and to check for possible paint effects, we returned males to their Petri dish and offered fruit flies ad libitum (Drosophilaspp.), registering prey capture and feeding. This procedure was performed during feeding days, so all spiders (manipulated and not) received fruit flies and had the same feeding regimen."