Mantisfly

Image: cotinis

It looks like a mantis, eats like a mantis, it might even fly like a mantis...

But it's not a mantis!

Image: Katja Schulz

They look like they could be twins but mantises and Mantisflies are very distantly related. Mantises are most closely related to cockroaches and termites while Mantisflies belong to that enormous group of insects which pass through the full, larva-pupa-adult metamorphosis. This means they're more closely related to bees, beetles and butterflies than they are to mantises.

You wouldn't think it to look at them! The long, slim thorax, the large eyes on a triangular head... What else? Hmmm...

Image: Isabel de Horna

Oh yeah! Giant, raptorial forelegs!

They of course are used to grab hold of prey in a spiky grip so the Mantisfly can eat without worrying about all the writhing and squirming and desperate attempts to escape. That kind of stuff is such a downer when you're simply trying to enjoy your meal.

Image: cotinis

Oh! And always, always, always look at their eyes. They're utterly magical with their kaleidoscopic colours like a million tiny opalescent mood stones. They're HYPNOTIC! So... maybe you should never, never, never look at their eyes.

There are about 400 species of Mantisfly or Mantidfly or Mantispid within a family called Mantispidae. Most of them live in the tropics and only a handful can make it in colder, more northerly parts. They range in length from a mere 5 mm (0.2 in) to a whopping 5 cm (2 in).

They belong to the order of insects known as Neuroptera, or Net-winged Insects, alongside the ubiquitous and unassuming Green Lacewings and the monstrous-when-young Ant Lions.

Video: Ed Kern

Some Mantisflies are just as green as a Green Lacewing, others are brown. Some try out fun, bright colours and patterns and there are also a few who make for very convincing wasp-mimics. They're harmless to humans, though. They have no sting and those big, beefy front legs are not effective against something our size regardless of how horrifyingly violent and gory they are for small insect prey.

But what about the youth?

Image: cotinis

Net-winged Insects don't get anywhere near the fame and attention they deserve for the wondrous and frightening forms of their larvae. Those beastly, blood-sucking Ant Lions are very well known, but what about the grotesque, blood-sucking Owlfly or the strange, straw-jaws of the blood-sucking Osmylid?

Mantisflies carry on the tradition of ghastly larvae but add a twist of their own: they're parasitoids!

To be clear, not all Mantisfly larvae are parasitoids. Some are good old-fashioned predators. Some are gluttonous parasitoids who pig out on the larvae of wasps and other insects. For quite a few Mantisflies the escapades of their early life stages are somewhere between not well known and completely unknown. There's no telling how interesting some of those stories may be, because the most famous Mantisfly life cycle is very interesting indeed.

Video: shyrching

It all starts when a female Mantisfly lays a gigantic number of tiny eggs on the side of a tree or leaf. Each one is attached to the surface by a silk stalk, probably to keep them out of reach of ever-inquisitive ants. It's a strategy they share with Green Lacewings. However, Mantisfly eggs are smaller which and the Mantisfly produces a lot more of them. This will turn out to be a good idea.

These Mantisflies are hypermetamorphic. In other words, they take metamorphosis and push it up a gear. While other insects go through a larva-pupa-adult cycle, hypermetamorphosis adds a step: larva-completely different larva-pupa-adult.

The point is that the two larvae have different jobs to do. The first one is tiny and has long legs so it can run around and find food. The second one has a soft, bulging body and almost no legs at all. It can do almost nothing but eat.

We've seen this method before with Oil Beetles. Just think about the effort some parasitoid wasps go to in providing for their young. They build nests, pack them full of paralysed cockroaches or spiders and only once a nest is fully provisioned with all the food a growing larva needs will they finally lay a single egg. Even flies look for carcasses or some other rot to serve as food for their young and place their eggs in the middle of it.

Image: Sarah Gregg

Mantisflies don't do any of this. They lay a huge number of eggs and expect their tiny larvae to go forth and find their own food. And only after they've done that can the larvae turn into the eating machines that fly maggots and wasp grubs start out as.

And just to add to the difficulty, these Mantisfly larvae have a very particular food requirement: spider eggs!

This is not a simple proposition. Spiders keep their eggs bundled up in silk egg sacs and many will guard them against predators. Some Mantisfly larvae will simply go in for an all out assault. They wander around until they find an egg sac and then set about gnawing their way into it. Perhaps they're just so tiny they escape the spider's notice.

Image: Carlos De Soto Molinari

Others are more crafty. They find an adult spider, jump on and cling to its body. If it happens to be a male, they wait around until he starts mating with a female and then jump on her instead. Then they wait around some more until the spider starts laying her eggs. Now they jump into the mass of eggs and hide as the spider surrounds them all in silk.

It can be a long wait for these larvae as they sit on the spider's body, so in the meantime they drink a bit of spider haemolymph (arthropod blood) to keep them going. Some will even march into her book lungs and wait there instead, as if it's some kind of reception area. The audacity!

Image: cotinis

Either way, it's easy to imagine that a lot of larvae will never find their way into an egg sac. It's a haphazard process and their mother makes no effort to help them. The ones that do make it, however, are completely surrounded in food and nothing but food. There's nothing else to catch their notice. There's nothing to do but eat. So they eat and eat and they turn into that flabby larva so they can eat some more. Then they pupate and develop into an adult.

Now, I'm sure we're all most familiar with butterfly pupae, known as the chrysalis. We see them stuck to a twig, completely unmoving and uninterested in the world around them, which is fine because they can't do anything about anything. But not all pupae are like that. Some of them bite and crawl. Mantisflies develop into one of these.

Video: nature1upclose

They become what's known as a pharate adult. The Mantisfly is a fully developed adult, but it hasn't escaped the pupa yet. It chews a hole in the wall of that cramped egg sac and walks away. Only once it has found an area with sufficient space to stretch a leg and flex a wing will it begin to emerge from the pupa.

The pupa is so adult-shaped it looks more like a cicada or a dragonfly, one of those insects that doesn't pass through a pupa stage at all. You would never have guessed the epic journey its gone through. From one among a massed horde of wanderers to blood-sucking spider parasite to egg-eating spider parasitoid.

After all that sin, it's no wonder they're shaped like a Praying Mantis!