I can’t believe they’re not wasps! (sesiidae clearwing moths)

This week I wanted to showcase an incredible family of moths that are known to mimic a variety of bees and wasps depending on the genera and species. It's not just their looks that are incredibly accurate though. It's the behaviors as well! 

 

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Transcript:

Welcome everyone to episode 57 of Insects for Fun! The weekly entomology podcast covering all kinds of interesting things in the world of entomology. Today we are doing a deep dive into clear wing moths, which are quite possibly the best wasp mimics I have ever seen. 

 

Let’s start with the basics, as we always do. Clearwing moths belong to the family sesiidae, of which there are around 165 genera, and over 1,525 species in the world. There are other families, but we’re just gonna focus on this one today and to be honest it has way more species than I was expecting. That being said it's time for a quick disclaimer! I just wanna quickly remind everyone that when we dive into families that are this size, it becomes increasingly difficult to say that any one characteristic can be found within each individual. So just remember, every species is gonna be a bit different! 

 

Alright so we have this family of moths called clearwings, but what’s so special about them? Well! These moths are daytime fliers for one, and are known for their incredible wasp mimicry. And let’s not forget those clear wings for which they’re named. You see these incredible creatures have evolved to mimic a variety of different wasp species. I'm talking about everything from yellow jackets to parasitoids, and the mimicry doesn’t stop at their looks. Even the flight and sounds they produce can resemble wasps, making them scary to many people who don’t even know they exist. This kind of mimicry is called batesian mimicry which is when animals that don’t have any special defenses of their own mimic ones that do in an effort to protect themselves. I suppose you could say that the ability to mimic something scary is a special defense although once you see through the bluff they’re in trouble. This is again one of those times when I strongly suggest you check out the instagram or fb pages because I’ll be posting images of different species, and they really are incredible. 

 

For starters the wings aren’t just clear but also shaped to look like wasps with most being more slender and triangular in appearance, and as I mentioned earlier there are species which evolved to sound like the wasps and bees they mimic. This is particularly known to be the case for southeast asian species of which two were tested acoustically and found to produce sounds very similar to the bees they mimic, but different from other bees. I just can’t get over how these moths have evolved to strictly mimic individual bee and wasp species as opposed to being more general. Here’s an audio clip of their buzzing: 

 

In 2020 Thailand a new genus and species was discovered which mimics a type of parasitoid called a braconidae. Unlike other mimics which rely on colors and body shapes, this one has marks on its wings which in flight make the body appear curved in the same way as a braconid wasp. Pretty crafty I gotta say. I’ll put a picture on the IG and FB pages. 

 

Now on the other side of the spectrum there is a wasp mimic moth found in central and south america which does such an insanely detailed job that it left me staring for longer than I should have. The species is called Pseudosphex laticincta and I’m gonna put the image up of this one next to the wasp it mimics as well because man or man it is incredible. 

 

Moving along to other incredible things, the caterpillars for sesiidae moths do not feed on the leaves of plants in the same way other caterpillars do. They don’t even look like caterpillars (huh) the moths lay their eggs on host plants but the caterpillars then burrow directly into the plants, and are never seen again… until they come out of course. But yeah seriously the caterpillars don’t have color, and barely have any legs either. Some of them honestly look like wasp larvae which again is truly wild. How can something in a separate order of insects evolve to look so similar! It’s not like these moths had a conference one day (conference noises) and said you know what? Things aren’t working out for us, but those wasps? They seem to have it good, so let’s just cosplay as those guys from now on. 

 

Actually in the most recent bonus episodes available on Patreon I do dive into something which could very well explain this phenomenon, and my patrons might actually know exactly what I’m talking about if they’re up to date, but enough about that, let’s see just how similar these moths take their mimicry… 

 

So we have these caterpillars that don’t really look like caterpillars, and they seem to feed on wood, roots, and other internal plant structures which again is not what your average caterpillar does, but this type of behavior is known within wasp and bee species so that’s another point for towards professional mimicry. As for how long it takes to complete a life cycle, that varies on the species, but most of them take 1 year to fully develop.

 

The larvae are actually well known pests to gardeners and people who work in landscaping, as well as forest management. The reason is simply that the larvae often damage the plants that they infest by weakening them to the point of losing branches or even death. Although any plant which has been heavily infested by clearwing caterpillars must have been weakened already by other factors because the caterpillars alone shouldn’t be enough to kill a tree. People in integrated pest management commonly abbreviated as IPM refer to these caterpillars as clearwing borers, and the standard protocols are to first make sure the problem is actually clearwing borers. Many insects will bore into trees, especially beetles, and the treatments differ depending on the insect. Common host trees include but are not limited to Alders, Poplars, Pine, Fir, Oak, Sycamore, Willow and stone fruit trees like apricot, cherry, peach and plum. Signs of borers inside a tree are gnarled or rough looking bark patches, swelling on branches, piles of dust and waste outside a tree, and pupal cases poking out of the bark. The hallmark for clearwing borers specifically would be the pupal cases. 

 

There are other moths with clearwings by the way which cannot be mistaken for wasps, like hummingbird moths for example, and I will definitely do an entire episode on those in the future. 

 

Before we wrap up the episode I want to quickly go into one particular species which got my attention and started this entire episode. That would be the hornet moth sesia apiformis which can be found across Europe and in Britain. It’s not often we find ourselves in Europe or the UK on this podcast, but that doesn’t mean I don’t notice what’s there! (notice me senpai). Anyway this large hornet looking moth can be found in parks, meadows, golf courses, marshes, basically anywhere really, and they prefer laying eggs on trees surrounded by vegetation. 

 

This moth is really cute despite being a mimic to the European hornet, and the females act pretty similar to a giant silkmoth meaning they’re pretty docile and won’t fly until after they’ve mated. I’ll of course post a picture of this one too. 

 

The larvae for these moths feed in the roots of trees unlike the others we’ve mentioned so far, and can spend up to 2 years before pupating. Our UK listeners can probably testify that the weather isn’t exactly ideal over there most of the time, with summers historically being pretty short, and as a result the larva have been known to grow slower than others. 

 

When the caterpillars do finally make their pupae it is within the tree and these ones are one of few within the family to create a cocoon. Inside this cocoon holds the pupa which for this species are lined with rings of small spines. The spines on these pupae cling to walls of the hole they bore in the tree’s trunk and create a grip which the pupae use to wriggle their way out in mid June or July. 

 

The moth was introduced into New England before 1880 and can be found in the northeastern parts of North America with detailed records around Ontario, Canada. 

 

And with that, this wraps up today’s episode on the clearwings moths in the family sesiidae. As always I hope you enjoyed it and learned something interesting! If you are enjoying the podcast it is highly appreciated if you drop a review and rating on whatever platform you listen. It helps me know if I’m doing a good job and is social proof to people who aren’t sure if they wanna press play or not. 

 

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