Scientists have documented a variety of strange ways in which some insects leech off of other larger insects. In many cases, this phenomenon could be accurately called parasitism, and it is not rare in the insect kingdom. For example, parasitic wasps may be the most species-rich insects on the planet, and other insects also rely on parasitism in order to survive. A group of insects known as “mantispidae” could also be considered parasitic considering their habit of feeding on larger-sized hosts and their eggs, but mantispidae larvae seem to be courageous insects, as they feed off of a particularly aggressive host that you would never want near your own mouth. The mantispidae larvae parasitize spider egg sacs, but in order to access egg sacs at the right time, they travel on the backs or undersides of large spiders while feeding on their blood when necessary.

The act of hitching rides on the backs or undersides of unsuspecting spiders is known as “spider-boarding.” Spider-boarding is practiced only by mantispidae, also referred to as “mantidflies,” and this behavior originated around 44 million years ago. Interestingly, Michael Ohl from Berlin’s Museum of Natural History, has recently found a 44 million year old fossil that clearly shows an ancient spider species with a mantidfly larvae located on the underside of its abdomen.

Mantidfly larvae are picky eaters, as they refuse to consume anything other than spiderlings or blood from adult spiders, but this blood is merely meant to hold the larvae over until they can successfully penetrate eggs sacs in order to devour unhatched, or in some cases hatched, spiderlings. In addition to spider-boarding, mantidfly larvae will jump from one spider to another while spiders are either mating or fighting. This ability is useful, as only female spiders possess the egg sacs that mantidfly larvae find so appetizing. While the larvae may ride on male spiders, they will only do so until it takes them toward females. Mantidfly larvae can spend months on their spider hosts. In fact, they can even overwinter on spiders before departing to invade insects come spring.

Do you think that spiders ever find and eat mantidfly larvae?