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Katydids and Didn’ts

2 Jul
Katydid nymph on a leaf.

Katydid nymph on a leaf.

Katydids are a member of the order Orthoptera (grasshoppers, katydids, crickets, etc.) and the family Tettigoniidae. Orthopteran nymphs, or immatures can be distinguished from adults by the development of their wings.  Only adult insects have completely developed wings (think butterflies, beetles, and flies).  Immature insects have not yet developed wings (think caterpillars, grubs, and maggots).  Katydids, like other orthopterans, have incomplete metamorphosis, meaning they lack a pupal stage (think chrysalis or cocoons).  Instead, the immatures generally resemble the adults in appearance, and partially developed stubby wings, called wing pads, may be present in some of the later molts.  The nymph above is very young, and has no wings or wing pads present.

Here’s a picture from my own backyard in Texas!

A katydid nymph on a leaf.

A tiny katydid perches on a leaf.

Katydids are also called ‘long-horned grasshoppers’ in reference to their long antennae.  Orthopterans of the suborder Ensifera, or ‘sword-bearing’, generally have antennae longer than their body length as well as exserted ovipositors (sword-like egg-laying tubes that allow females to saw their eggs into plants or insert them down into the fround.)  Thus, katydids (like crickets) can be distinguished from grasshoppers by their long slender antennae and legs.

Below, you can see a grasshopper nymph, from the suborder Caelifera.  This grasshopper is a member of the family Acrididae, the ‘short-horned grasshoppers.’

A grasshopper nymph perched on a fingertip.

A grasshopper nymph perched on a fingertip.

Stick Mimic

31 May
A stick grasshopper on a flower.

A stick grasshopper on a flower.

Look twice.  That’s not a stick.  It’s not even a walking stick.  It’s a grasshopper!

The stick grasshoppers comprise the family Proscopiidae, and are unique to South America.  Aside from their jumping hind legs, their heads are very distinct from that of a walking stick: elongate, with a mouth near the bendable neck, and eyes further along the length of the head.

These guys were all over Argentina and fun to watch.  This particular fellow was posing on a flower all by himself, so I had to snap a picture.  Here’s another stick hopper, this one particularly cryptic:

A well-camouflaged stick grasshopper in Argentina (Proscopiidae).

A well-camouflaged stick grasshopper in Argentina (Proscopiidae).

Boys and Girls – Sexual Dimorphism in Lubbers

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

Sexually dimorphic male and female grasshoppers mate.

Found this mating pair at a field site in Argentina.  We saw these guys all over.  The females of this species are huge for grasshoppers, palm-sized and heavy.  The littler male looks a bit ridiculous perched on top. My labmate Paul calls these guys the ‘chubby chasers.’

This male and female  Staleochlora exhibit a strong example of sexual dimorphism: the adult female is much larger than the adult male of the same species.  This is common in insects, where the female’s large body size allows her to hold more eggs internally.  Cut a female grasshopper open and you will see she is literally stuffed with eggs up to her thorax.  In lubber grasshoppers (family Romaleidae) adults are often so large they can no feasibly support flight, and the wings are reduced.  For this reason they are considered ‘landlubbers.’  This male lubber can still fly fairly well to seek a mate and avoid predators, but the female must rely on her cryptic coloration and limited jumping ability to avoid becoming a meal.

My mother always asks me why entomologists are so found of ‘bug sex’ pictures.  (I got her an insect field guide and many of the photos resemble the one above.)  Aside from the somewhat warped humor value of shots like the one above (well I think it’s funny) pictures like this also provide a handy side by side comparison of males an females.  Such a reference is especially important when insects are highly sexually dimorphic.  Encountered separately, the casual observer (such as myself, unaided by grasshopper specialist Paul) would probably assume the two insects above were completely different species.

Of course, a secondary reason for the abundance of photos is that mating insects are generally fairly slow and less prone to jumping away from looming camera lenses.

Palm sized female grasshopper.

Palm sized female grasshopper.

Grasshopper and Spines

30 Apr
Grasshopper being artsy.

A grasshopper perches on a spiny plant.

Spotted this guy striking an artistic pose on a spiny plant at an Argentinian field site and had to snap a photo.

A male lubber grasshopper (family Romaleidae) of genus Staleochlora. More on these guys next week!

Your insect vocab of the day is ‘arolium.’  This is the pad visible between the two claws at the end of the front leg.  This structure acts as a suction pad, producing a sticky secretion that enables the insect to climb smooth surfaces.  Not all insects (or even all grasshoppers) have this structure.

Ant Picnic – Acrobat Ants

16 Apr
Acrobat ants feeding on katydid.

Acrobat ants (Crematogaster) feast on a katydid.

I discovered this grisly scene by following a trail of acrobat ants across the red brick courtyard of our Argentinean hotel.  Hundreds of worker ants trekked nearly 20 meters from their nest to the scene of the massacre where they joined their sisters in chewing through the katydid’s tough exoskeleton to burrow their way into the soft tissue beneath, carving up their kill to bring food back to the nest.

Acrobat ants (genus Crematogaster), are typically arboreal, or tree-nesting, ants.  Their petiole, or waist, connects to the top of their heart-shaped gaster (the third body region of ants).  This allows them to flip the gaster up over their backs, both for balance while navigating their tree habitat, and defensively like the stinger of a scorpion.  Acrobat ants wield their venom in a defensive spray rather than a stinging injection.  This is an effective weapon of chemical warfare against other arthropods and small organisms, but generally passes unnoticed by humans.  Their mandibles can still deliver a pinch, however, and they will attempt to follow a bite with a spray of formic acid into the wound.  Although I took this picture in Argentina, acrobat ants are relatively common across the United States.