Ensign Wasp

Image: Muhammad Mahdi Karim

Uh oh... someone's been playing around with the shrink ray.

There are over 400 species in the Evaniidae family, found all over the warmer parts of the world.

Image: Leonardo Ré-Jorge

They're extraordinary to look at. With their long antenna, long hindmost legs, bulky thorax and weirdest of all, their tiny, tiny abdomen.

Like ants and other wasps, the abdomen is split into a bulging gaster and a tube called the petiole. But few have quite so tiny a gaster and so long and narrow a petiole. It could've made them look rather petite and delicate were it not for the tremendously beefy thorax it all sprouts from.

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Video: Diego da Cruz Pereira

Things get even stranger when you see them in life. The antennae vibrate in nervous excitement while the gaster is continually pumped up and down for some reason. No wonder its so slim if they give it that kind of workout all day!

It's also why members of this family are known as Ensign Wasps or Hatchet Wasps. It looks like they're swinging a miniature flag or hatchet all the time. If you got it, swing it.

Image: Marc AuMarc
Evania appendigaster

While the family as a whole can be found across the world, one particular species has acquired tremendous success all for itself. Evania appendigaster is thought to have originated somewhere in Asia but has since spread across the tropics and even into some temperate zones.

It's pretty big, too! Nearing an inch long with those legs and antennae.

Most Ensign Wasps haven't been researched in detail but the few that have are all cockroach parasitoids. An egg is laid in an ootheca, which is a protective cocoon full of the cockroach's eggs. The ootheca is tough, so our Ensign Wasp takes her time selecting a good one and perhaps finding a weak spot. Then she spends up to half an hour drilling into it so she can lay a single egg within.

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Video: imagoUFRJ
1:06, appalling

The egg soon hatches to reveal a ravenously hungry larva that feeds on all the cockroach eggs, growing ever more obscenely plump with each mouthful. In the case of E. appendigaster, its mandibles will even change as it grows. The finely serrated affair it starts out with helps to cut into the cockroach eggs. The next pair lose the serration and are longer, with three teeth on each. The final set has only two teeth, one narrow and curved the other long and blunt.

I love those kinds of tiny details! Who knows what other strange precision might be going on in other tiny creatures if only someone took the time to take a really close look?

In any case, that flabby larva soon pupates to develop into an adult Ensign Wasp which chews her way out of the dark, claustrophobic casing of the ootheca to emerge at last into the open. She stretches her long legs and antennae. She pumps her slender gaster up and down. It must be quite a relief after all that time filling out what was basically a coffin with her rolls of flabby, larval flesh.