Perhaps this fascination originates in our ontogeny: we, like all viviparous creatures, play host for our gestating, "parasitic" fetuses; and they suck away our vitality and alter our behavior (i.e., cause us to host baby showers and purchase adorably tiny shoes) for nine long months. ("Us" being mothers, of course. And, no, I am not a mother, or even a female. But anyway...) This grotesque mystique is what engenders such works as (for example) the "Alien" franchise, and ensures their continued popularity.
Of course, any biologist worth his snuff knows that the eponymous extraterrestrial of the said horror franchise (fig. 1; drawn by H. R. Giger) is unequivocally not a parasite. It kills its host (in grisly fashion)--not by occasional accident, but by necessity. Therefore, it is a parasitoid: and parasitoids are infinitely more disturbing than true parasites.And insects (my particular area of expertise) harbor a wide range of parasitoids. Indeed, the 60,000 species of ichneumon wasps (Ichneumonidae), and the remainder of the panoply of parasitoid wasps, are perhaps the best-known exemplars of the lifestyle: a lifestyle whose prevalence was cited explicitly by Charles Darwin as evidence against a benevolent Creator (Gould, 1994). But I wouldn't post about something well-known, now would I? No; instead I will discuss some parasitoid wasp families that I think are sadly obscure.These families are included within the Aculeata--the clade of the order Hymenoptera consisting of those wasps (to use that term in a phylogenetic sense) that possess a stinger (a diagram of one can be found at right). As the organ is a specialized ovipositor, only females bear one (although a good deal of lineages have secondarily lost theirs). A stinger is a versatile instrument: one can use it for self-defense, to kill prey, subdue a rival, or even as an impromptu shish-kebab for carrying said prey back to one's nest (as Oxybelus sp. do; Peckham, 1985). Consequently, aculeates run a gamut of lifestyles: some are parasitoids that use their stingers to stun their offsprings' hosts; others use theirs to paralyze prey that will be hauled back to a burrow, where the individual will be devoured by the wasp's larvae; and still others use it in the service of their colony.Three superfamilies comprise the Aculeata: Chrysidoidea, Vespoidea, and Apoidea; all include some parasitoids. Interestingly, all aculeates who grow in that manner are ectoparasitoids: that is, they live and grow as larvae on their hosts' bodily exteriors (in contrast to most hymenopteran parasitoids, who dine from the interior). All of them, that is, except the members of two related families: the Dryinidae and Embolemidae.