The spider that 'manipulates' fireflies to attract more prey

A recent scientific study published in Current Biology, has shown that Araneus ventricosus, a spider of the family Araneidae widespread in China, Japan and Korea, has devised a particularly ingenious strategy for hunting: "It 'exploits' the bioluminescence of its favourite prey, the fly, using them as bait in order to lure other specimens into its web. The most curious and interesting aspect is that all the firefly specimens caught are only males, although the females also 'glow' in the dark of the night. But why does this spider prefer male specimens and not female ones?

According to the findings of the study, the main prey of Araneus ventricosus are males: in its webs, female specimens are virtually absent. Moreover, the study showed how males of Abscondita terminalis, a firefly native to Asia characterised by having specimens of both winged sexes, behave like females once trapped in Araneus ventricosus's web. How? By using the recognition light signal typical of mating females, when they want to attract other males. Usually the latter use two different light signals to attract females, but once caught in the Araneus ventricosus web they strangely change their behaviour.

But why do they behave like females in this case? Well, Araenus ventricosus manages to control the way males of Abscondita terminalis use light, forcing them to behave like female specimens. This stratagem allows it to attract other males, who are trapped in the web, becoming prey in turn. The spider then performs active manipulation, immobilising the firefly with a combination of bites and silk 'bandages', prompting it to imitate the behaviour of the females. It remains to be seen whether this is done through purely mechanical manipulation, or whether the venom transmitted by the bite contributes to modifying the behaviour of the predates.

In the world of arachnids, we can mention another ingenious and alternative predatory strategy, that of the orc-faced spider (Deinopis spinosa), belonging to the Deinopidae family. These spiders tend to construct their web by weaving it with their front legs and then throwing it at prey, trapping them. This tactic is used by the entire Deinopidae family, but the ogre-faced spider has developed a further strategy, thanks to which it also captures prey in flight. In fact, these spiders are able to perceive insects in flight up to two metres away, thanks to a special organ positioned at the tip of the hind legs that can sense the vibrations and, consequently, react. The spider then jumps backwards and immobilises its prey, as also confirmed by a scient study

There are also some species of spiders that carry out veritable ambushes to catch their prey. These include the tarantula (Theraphosidae) or the wolf spiders (Lycosa). Their strategy is to build their tana directly on the ground, in a strategic position from which they await the arrival of prey. In doing so, they are able to attack so quickly that the victim does not even have time to react. Among the prey of these spiders are not only insects, but also small rodents: they have such a strong and robust body structure that they are able to immobilise them by injecting them with a lethal dose of poison.