Killer fairies

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I’ve been hoarding these photos for a little while; I haven’t actually seen a mantis for perhaps a week or two, though there was a period in August and September when they were relatively abundant, like the grasshoppers. After I’d been observing them for a little while, I finally got around to getting some photos of them. But then the photos sat on my hard drive for some time longer, as I posted about other things, or didn’t post at all when I planned to. I find life has an unfortunately habit of distracting me from the blog. I suppose, on the flip side, the blog has a habit of distracting me from the rest of life, too, so perhaps it all balances out.

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I almost never find mantises just sitting; usually when I spot them it’s because I’ve disturbed them from the grass and they go fluttering off to another spot some distance down the trail. You can always tell when it’s a mantis flying away from you – they have thin, delicate wings, long and rounded, that catch the light just so as they fly. They look like fairies, long slender bodies hanging between shimmering gossamer wings. I wouldn’t be the least bit surprised if the legends of fairies were begun by people seeing mantises flying away from them.

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I took photos of two individuals. In both cases I watched them fly away and noted where they came to rest again. By carefully sneaking up on the spot I was able to locate them among the grasses and godenrods before they flew again. Although there are about 20 native species of mantis in North America, the most common species, at least in areas I’ve been, is introduced. It’s the European Mantis, Mantis religiosa, native to the Mediterranean and adjoining parts of Asia. I’ve seen different stories for the explantion: one that suggests it arrived accidentally on a shipment of plants, another that claims it was introduced as biological control. Ironically, it’s the official state insect of Connecticut. It can be told from our native species by the presence of black-and-white “eye spots” on the inner surface of the upper foreleg. There are two colour variations, a green and a brown. Just by fortunate chance, I happened across one of each colour morph.

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The mantis’ claim to fame is really in its forelegs. These appendages not only give it its common name (“praying mantis”) for the activity called to mind when the insect is at rest, but are also deadly tools for catching and killing prey. The secret is in those sharp, curved talons that protrude from halfway down the foreleg. The mantis’ foreleg looks like it stops at the claw and the thin part beyond resembles a long pinky finger being held delicately aloft. Really, though, the thin part is the normal foreleg, and it’s just the upper part of the leg that has been modified. The mantis still walks on the long thin part of the leg (see above photos). Many insects have hair-like protrusions from their joints, and I presume the spur of the mantis is a modified one of these. As I’m sure you can guess, the claw is used for spearing prey, and for hooking and dragging prey back to the body. Mantises are strong – they can spear a hummingbird with those sharp claws and hold it, suspended, while they eat.

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Unless the prey is very large, though, it isn’t the spur that holds them after capture. Rather, it’s the series of sharp spines that line the inside of the mantis’ leg. You can see the long spines along the middle segment and the shorter tooth-like jags on the fore-segment in the previous photo. When the mantis folds its leg, the prey is pressed into the “teeth” and held there. In doing some searching round the ‘net for mantis info, I found this photo at the arboretum of my old alma mater that shows a mantis holding a grasshopper. The “pinky finger” folds up out of the way while the claw is in use.

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Praying mantises have huge eyes for the size of their head. Just like dragonflies or other predatory insects, mantids are strongly dependent on their vision for detecting and capturing prey. I’m not sure whether there’s a purpose to the stripes that cross through the eyes or not; they may simply be a form of camouflage, to break up the insect’s outline. Mantises are leaf/twig mimics, their shape and posture blending them in with their substrate both in order to hide from predators and to fool potential prey.

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As vertebrates ourselves, and mostly used to seeing other vertebrates up close, we tend to think of mouths as being two-jawed – an upper and a lower. Insects, however, usually have three: one upper jaw or lip (called the labrum), and then two lower jaws (called the mandibles) that can open and separate to the sides. In addition to these, insects have a second set of separable appendages near their mouth, called maxillae, which function much like vertebrates might use a tongue, to manipulate food items. And underneath all this is the floor of the mouth, the labium, which basically just prevents the foot from falling out.

My interpretation of the mantis’ mouth here is that there is one tooth-like protrusion coming up from the bottom which is the labium; a thicker, darker red bit just above which is the mandible; a thin, multi-segmented appendage that is the maxilla; and then the nose that you can’t really see the end of, which is the labrum.

And no, I don’t think you can tell the sex of the mantis by whether or not it’s wearing lipstick.

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Mantises are known for their reputation of “sexual cannibalism”, but the validity of this behaviour is debated. It’s been observed, sure – but mostly in the laboratory. Some argue that because mantises are highly visual insects, their behaviour is affected by the presence of people, and that cannibalism may be the result of distracted males, irritated females, or some other human-created cause. It’s rarely observed in the field, but it’s hard to say how much of that is because it doesn’t normally occur and how much is simply that it’s rarely observed. If the behaviour is accepted as valid and normal, then the next question is why does it occur. The leading argument there is that it lends a selective advantage to the male to be eaten because males whose heads have been removed end up copulating longer, and have a higher rate of fertilization, than those that are not cannibalized. Also, by eating the male the female may boost her metabolism and nutrients, leading to more and healthier eggs.

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After mating, the female will find a sheltered nook in which to lay her eggs. When freshly laid, the eggs are in a soft, frothy cocoon that gradually hardens into what looks a little like a tiny pouch with a zipper up the middle. I found some last spring, and posted a photo of one here. They eggs overwinter in these, and hatch out in the spring. The young mantises spend the summer growing up before mating in the fall. If you happen to find an egg case, you can bring it in and overwinter it in a dry spot at the back of your fridge, much as you might do with a caterpillar cocoon. Bring it out and set it up in a terrarium in the spring, and watch the babies hatch and grow. Or, if you haven’t stumbled across an egg case you could collect, you can order your own mantis-raising kit from Discover Channel’s online store.

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Homes for the winter

Cecropia moth cocoon

Here’s some of those photos I’ve had sitting around for a while, waiting for an opportunity to post about them. This first one I’ve had since January! I came across this interesting structure while out with Blackburnian during the Colour-coding Chickadees walk. I had no idea what it was at the time. It was already open when I came across it, and there was nothing in it. It resembled a cocoon, but I didn’t really know. Lots else to post about, so I never got around to looking it up.

Then in mid-February, Jennifer over at A Passion for Nature posted a cocoon she’d been seeing on some of her walks, and a couple days later she posted a follow-up about the cocoon’s occupant. Turns out, it’s the cocoon of a Cecropia Moth, one of the North American silk moths, a group of beautiful, giant moths whose caterpillars spin “silk” which they use to create their cocoons. Jennifer directs her readers to a rather amazing site that documents the life cycle of the moth from egg to adult (and now I’ll direct you there, too!). The site indicates that the moths overwinter as pupae, so the fact that this cocoon is split open likely suggests that it’s either last year’s case, or somebody/thing got to it before I did this winter.

Bagworm moth case, Psyche casta

This second one is also a moth, and I’ve also had it on hand since January. I knew right away what this one was when I saw it, from having browsed through the Moth Photographers Group website while identifying a few moths last fall. Of course, I couldn’t remember exactly which it was, just that I’d seen it on the pages, so I had to go back and scan through their many (very useful) pages all over again.

The case, which superficially reminds me of those made by caddisfly larvae, is made by a moth belonging to the group of “bagworm moths”. This one’s probably Psyche casta; the different species have different case styles, but I would assume some of them to be subtle. Like the caddisfly, the moth larvae tote this bundle of sticks around with them until it’s time to pupate, at which time they affix it to a solid surface for the winter. I found three of these all sitting in the window frames of my parents’ house. Two were between the panes of glass, but this third one was on the interior frame, which made it easier to photograph, but also meant it was exposed to spiderwebs, dust, pet hair, etc.

Wikipedia indicates that many bagworm moth females have vestigial wings, and sometimes never leave their cases, mating with males even while still inside. They die after mating, either having laid the eggs inside the case, or without having laid the eggs (so the larvae mature and emerge from the female’s body). The eggs are very hardy, and a bird that finds the case and eats it will pass the eggs through its digestive system intact, aiding in the spread of “new blood” from one area to another.

Praying mantis egg case

And this final case isn’t a moth or butterfly cocoon, but instead was created by a Praying Mantis. They started appearing late last fall, and I think I found five in total, four of them laid on the research station’s exterior walls. I didn’t know what this was at first, either, but I think one of the volunteers at the station pointed it out and identified it for me. They were still there, all of them, when I was back for the start of the spring season. When they were first laid they were a little gooey to touch; now they’re all quite hard.

I read somewhere that they’re always laid on the south side of the object they’re affixed to, which is actually true of the four on the station building. The one pictured here, however, found at the base of a metal signpost, was on the north side. I guess that one didn’t get the memo. Mantids are fairly common at the spit, which is pretty neat, since I never saw many growing up. Despite their slightly startling, ferocious appearance, they’re pretty tame to pick up and handle, not inclined to bite, which makes them great for showing to kids. Just like hatching a cocoon, you can bring these cases inside and set them up in a terrarium to hatch – or, if you don’t want to risk damaging the wild ones, you could order your own Praying Mantis Encounter from Discovery Channel’s store, and treat the kids (or yourself) to a neat experience watching them grow. Only available to the US, unfortunately, or I’d order one! :)