Spongillafly

Image: Gilles San Martin

It's time to delve yet again into that beguiling order of insects known as Neuroptera, the Net-winged Insects.

This time we're looking at Spongillaflies, also known as Spongeflies. They have not only secured for themselves an exceedingly unique source of food, but their larvae are also real crafters.

There are about 60 known species of Spongillafly in the world, all belonging to a family called Sisyridae. They're active at night or twilight and are tiny, with a wingspan of 1 cm (0.4 in) across at most and sometimes less than half that. Their minute form retains the complicated, lacy wings and giant, sparkling eyes common among Net-winged Insects.

Image: Gilles San Martin

Adult Spongeflies are unfussy eaters. They can feed on tiny insects (like aphids), the carcasses of tiny insects (like dead aphids) and also honeydew. That's the sweet, sugary stuff excreted by certain sap-feeding insects (like aphids) and so beloved by all those shepherding ants.

Basically, aphids are like a conveniently soft, yielding tin of dinner and desert. And when they've had enough of that, they can move on to a feast of pollen. Lots of options. But it wasn't always like that for our little Spongefly.

They start out life as a collection of eggs left on plants above a lake or stream and protected by silk webbing laid down by their mother. When they hatch, the larvae drop into the waters below.

Image source
Larva

They're chubby little things, with spindly legs and weird mouth parts that look like a pair of flexible syringe needles. In fact, they look a lot like the larvae of their relatives, the Osmylids.

Once in the water, they can crawl or flap their bodies to swim as they seek out something to eat. I don't suppose you need to ask what their food source is, do you?

Image: Oleg Kirillow
Spongilla sp. a freshwater sponge

It's sponges, of course! Freshwater sponges, especially those belonging to the genus Spongilla. So it is that Spongeflies are one of those insects that are named after what they eat. Like Antlions and Dung Beetles. But not Dragonflies (the Heroic Knight Union would never stand for it) or, God forbid, Damselflies and Houseflies.

It's a tough break for the poor old freshwater sponge. Of the 5,000 known species of sponge, only a couple hundred live in freshwater, all the others are marine. They feed by filtering bacteria and other tiny edibles from the water, same as any other sponge, but they have had to adapt to their new, more fickle environment. After all, when a lake freezes over it's called Winter. When the sea does the same it's called an Ice Age.

So, despite being animals, freshwater sponges produce a kind of "seed" known as a gemmule. When the weather turns sour and the mother sponge dies, these gemmules act like survival pods. They're hardy enough to survive adverse conditions, ready to grow into new sponges when the time is right.

And after all that, a load of maggoty Spongeflies will be eagerly seeking them out. The little blighters crawl all over them and pierce their flesh with those weird, needle mouth parts. Then they suck out the internal fluids and the poor sponge can do nothing about it.

I can't help but have a sneaking respect for the larval Spongefly. They've tapped into a unique food source, an animal that almost acts more like a plant, and now they're sucking out its juices like... like... like an aphid on a rose bush. Something their parents might have eaten!

Eventually, after several weeks to a year, our larval Spongefly must think about becoming an adult. They leave the water and wander into some nook or cranny among rocks or tree bark. Arts and crafts soon commence.

Video: Animal Wire

It begins to weave an amazing outer mesh around itself from silk. Put some glass panes into the holes and you'll have a nice modern building that people will hate for a few years before getting used to it and then falling in love with it.

It then spins a silken cocoon and pupates.

Image: Vmenkov

Soon it will chew its way through the inner cocoon and the outer mesh wall to emerge as an adult. After all that time spent as a sponge parasite I hope they'll go on at eat a lot of plant parasites (like aphids). After all, if you are what you eat, then you eat what you are.