Among the Clover – Aquatic Grasshoppers?

A crested grasshopper (Xyleus sp.) in a flooded clover field along the Paraná river.

Happy St. Patrick’s Day! (And happy birthday to my brother, Eric.)

The grasshopper above is a member of the lubber family Romaleidae, genus Xyleus, a crested grasshopper.  We encountered a number of these large fellows doing field work in Argentina last year.  While we were there, frequent rains caused flooding in most of our field sites along the Paraná river.  This made working with fire ants difficult.  In one notable instance we returned to a line of sugar baits the following day and found tadpoles swimming around them.  Not optimal for a fire ant foraging study.  We also got to observe lots of insects coping with (and flourishing in) the flooded conditions, as in the case of the grasshopper pictured feeding half underwater below.

Thanks to Paul Lenhart for photos, IDs, and being awesome!

Rhammatocerus sp. grasshopper feeding in a flooded field along the Paraná.

Color Lubbers

An aposematic lubber grasshopper from Argentina (Romaleidae)

Some of my favorite Argentinian insects were these large, colorful lubber grasshoppers.  They were certainly striking, and easy to spot with the aposematic coloration they use to warn predators that they are poisonous.  Lubber grasshoppers belong to the orthopteran family Romaleidae, so named from Greek “romaleos” meaning “strong of body” in reference to their generally large size.  The term “lubber” may also be in reference to the old English use of the word to mean “clumsy” and “stout.”  Many lubber grasshoppers also have shortened wings, especially in the females, as we’ve seen previously, and are poor fliers and slow hoppers due to their heavy bodies.  In the case of this lubber grasshopper, any slowness or clumsiness due to body size is compensated by toxic chemicals that make them distasteful to potential predators.

An aposematic lubber grasshopper in Argentina (Zoniopoda inheringi).

Boys and Girls – Sexual Dimorphism in Lubbers

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.

Grasshopper and Spines

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.