Kapala ivorensis
No, the image is not that of a flying machine from the early 1900’s. For one thing, this week’s insect does fly, though, sadly, I’ve never been lucky enough to see it do so. No, this is the wasp Kapala ivorensis (Family Eucharitidae) a stunning representative of the relatively small percentage of insects that successfully attacks and kills normally aggressive ants. Moreover, it does so in the ant’s own nest. It manages this seemingly impossible feat not by a frontal attack but rather by following a strategy that involves hitching a ride on a worker ant, thereby gaining entrance to the nest. Before that happens however, gravid females fly around the vegetation near the nest entrance, stopping to deposit eggs directly onto leaf and flower buds. When the egg hatches a strange 1st instar form emerges called a “planidium”. Planidia differ from your average run of the mill worm-like wasp larvae in being heavily sclerotized and quite active, although lacking legs. What are the chances that a planidium is able to attach itself to a worker ant? Probably pretty meagre and a problem solved by the prodigious egg-laying ability of Eucharitidae females, some of which may lay 10,000-15,000 eggs (the single Kapala species for which data is available was carrying 4500 eggs when captured). Once inside the nest, the planidium enter the brood chamber and hops onboard a mature ant larva. There, the parasitoid waits until the ant begins to pupate at which time the parasitoid attacks the pupa and begins imbibing the host’s tissues and fluids. This process continues while the parasitoid passes through two further larval stages, finally pupating and emerging as an adult wasp, the ant itself left as a mere empty husk. The final step for the parasitoid is to find the nest entrance and escape to the outside. There is some evidence that the parasitoid evades host-ant defences by mimicking the cuticular hydrocarbon profile of the host which is close to that of the parasitoid. Ants may not recognize the parasitoid as “other”. Worker ant hosts have been observed carrying recently emerged adult Kapala out of the nest, in a non-lethal manner. The worker ant carries the wasp by grasping the long, paired frenal spines of the parasitoid, dumping it outside the nest entrance in a manner that has been described to be much like that of taking out the garbage.
Some other notes:
What about those terrific antennae? As is true for a great many of the thousands of wasp species, males have modified antennae. However, Kapala’s greatly expanded, branched antennae do stand out from the crowd. These are presumably of service in mate recognition and location. In contrast, female antennae are usually simple, lacking modifications.
Worldwide there are 16 species of Kapala, most of which are endemic to the Neotropics (South and Central America). Only a single species (Kapala ivorensis) has been recorded from the Afrotropical region. However, that species is widespread and relatively common so your chances of finding it are pretty good if you sample around ant nests.
Credits: Dr Robert Copeland