Male and Female Roesel’s Katydids
August 23, 2012 was a big day for us as far as catching lots of insects. We were giving another insect presentation at the Portage Lake District Library that day, and so (among other things) we went out sweep-netting in the tall grass all along Clover Weevil Road, clear back to the swamp in the woods, until we caught enough random small arthropods to fill three of our 12″x12″ screen-sided insect cages. So, after the presentation, I sat down with the girls and the camera, and we went through getting pictures of as many of the different species present as we could [1]. This included a species of katydid different from the big, green, leafy-looking ones that I’ve posted in the past:
The first one is a male. You can tell because he has claspers at the tip of his abdomen instead of an ovipositor.
He was also willing to sit on my finger, and glower menacingly at the camera.
Here’s a closeup of his genitalia, which look rather spiky and unpleasant.
He appears to be a Roesel’s Katydid, Metrioptera roeselii. This is a European species that somehow got transported to the US, and was spotted in Montreal in 1953. They have since spread through southeastern Canada and the northeastern US, at least as far south as Illinois.
This next one looks like a female of the same species. She’s got the same dark-colored pronotum[2] with yellow trim, the same row of three yellow dots on her side just behind the pronotum, and the same long jumping legs.
We can see that she’s a female, though, because instead of the male’s spiky genitalia, she’s got a fairly long, sword-shaped ovipositor at the tip of her abdomen.
She uses this ovipositor to inject her eggs into grass stems.
My specimens here have stubby wings, but there is a second form with long wings that normally only makes up a few percent of the population. The long-winged form is more able to travel long distances, and so when the conditions are bad the long-winged ones become more numerous because they are better suited for getting out and going where conditions are better. This is apparently triggered by their growth rate – if they grow slowly due to a shortage of food, then the wings have more time to fully develop. When there isn’t so much pressure to disperse, the short-winged form dominates because they devote less resources to wing growth, and so can lay more eggs.
They like tall grass in wet areas. The males sing, and their song is reported to sound a lot like the hum of overhead electrical transmission lines[3].
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[1] There was a lot of duplication. For some of the species, we had dozens of specimens. There was also a fair bit of attrition in the cages overnight, because there turned out to be a high proportion of predators in there.
[2] The pronotum is the hard shell on the back and sides, just behind the head and in front of the wings.
[3] Come to think of it, we caught these pretty much directly under the high-tension transmission lines that run through the woods out back. I wonder if they get drawn there by the line hum? Then again, it was tall grass on damp ground, which is supposed to be their preferred habitat anyway.
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Good morning,
I hope this e-mail finds you well. I was hoping to get some clarification on the differences between the last instar stage and adult stage of a female Roesel katydid. The late instar stage and adult form seem very similar (both have short wings and ovipositor present), so was hoping to ask you if there was a specific characteristic that could tell them apart?
Any insight on the above is very much appreciated!
Thank you,
Deanna
Deanna: I’m afraid I don’t know how to tell the short-winged adult from the final instar before adult, either. The biggest problem would be finding some where I could positively state that they *were* actually not in their final instars yet, so I could look for differences.
Thank you kindly for your response. I also meant to ask this question above – can the short-winged Roesel adults fly (in comparison to the long winged which seem to use them for dispersal reasons), or do they just use them to increase their jump lengths/stabilize themselves while jumping?
Thanks so much!
I wouldn’t think the short-winged ones would be able to fly. The ones I took the pictures of certainly didn’t do anything other than jump in a pretty ballistic sort of way.