Hopper Babies – Distinguishing adult and juvenile orthopterans

20 May
Katydid nymph on a leaf (Tettigoniidae).

Katydid nymph on a leaf (Tettigoniidae).

I found this impressively large katydid nymph hanging out at a gas station.  I thought he provided a particularly clear illustration on the difference between adult and juvenile wings in grasshoppers, katydids, etc.  Adult and juvenile orthopterans can generally be distinguished by the presence or absence of wings.  However, like other hemimetabolous insects, juvenile grasshoppers and co. gradually develop their wings as they move through larval molts, so later instars have signs of small, developing wings (wing pads or wing buds).  Moreover, some orthopteran species are brachypterous (short-winged) or apterous (wingless) as adults, further complicating the matter.  In collections, which generallly exclude immature insects, such species are notoriously underrepresented.

So the question is, how does one distinguish final instar grasshopper and katydid nymphs (those in the last juvenile stage prior to adulthood) from short-winged adults?  Here’s the trick as I learned it from my labmate Paul Lenhart.

Final instar katydid nymph grooming its hind leg (Tettigoniidae).

Final instar katydid nymph grooming its hind leg.

It took me a while to develop an eye for this, but the principle is fairly straight forward.  In the last nymphal instar before adulthood, orthopteran wings “flip.”  The hind wing (eventually to become the large, fan-folded flight structure) sits on top of the forewing (the elongate leathery tegmina which will protect the hindwing in adulthood).  You can see this in the picture above.  The main, costal vein of the hindwing is located dorsally (at the top), with a fan of veins running downwards, giving the characteristic “D” wing shape of a nymph.

A small male and large female grasshopper of the same species.

Sexually dimorphic male and female grasshoppers mate.

After the molt to adulthood the wings flip again, tucking the hindwing under the forewing with the costal vein now located ventrally (to the bottom).   Compare wings of the katydid nymph above to the more elongate, “U” shape of the forewing seen in these adult male and female lubber grasshoppers. The  veins in the short forewing of the brachypterous female run mostly parellel, rather than fanning downwards.

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4 Responses to “Hopper Babies – Distinguishing adult and juvenile orthopterans”

  1. budak May 30, 2011 at 4:42 am #

    that’s a very useful tip for fieldwork, thanks.

  2. Catherine May 8, 2012 at 3:17 pm #

    What kind of katydid nymphs are pictured?

    • 6legs2many May 25, 2012 at 3:29 pm #

      I don’t know. I’ll ask Paul.

    • 6legs2many May 25, 2012 at 4:29 pm #

      Paul Lenhart says:

      Those are nymphs of a true katydid (Pseudophyllinae). If you found them in the hill country they are probably the Truncated katydid Paracyrtophyllus robustus which is currently outbreaking there. They can be at high densities and in these conditions they are often purple. If you found those nymphs east of the hill country there are probably Pterophylla camellifolia the Common True Katydid. This guy is where the name katydid comes from (the sound of the call katy-did). You can hear it and other katydids here: http://entnemdept.ufl.edu/walker/buzz/
      Based on the shape of the pronotum it looks like the latter.

      If I remember correctly I found this fellow at a gas station between College Station and Houston (east of the hill country) so looks like I got myself the truest of katydids. 🙂

      Thanks for your question, Catherine, I learned something new.

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