Thursday, July 24, 2014

Blue-legged Grasshopper

This spring, Colorado Springs received consistent precipitation for the first time in several years. The rains resulted in lush plant growth and a corresponding explosion of grasshopper abundance and diversity. Some species I have not seen before, including the subject of this week's "OrThoptera Thursday," the Blue-legged Grasshopper (Metator pardalinus).

This beautiful animal is hard to mistake for any other grasshopper. The streamlined body is "leopard-spotted," a pattern common to many other species, but the hind femur is proportionately longer and more slender than in other band-winged grasshoppers. The inside of the hind femur, and the hind tibia, are bright blue. The abdomen can also have a flush of blue. The hind wings, exposed in flight, are bright red, pinkish, orange, or yellow, with a bold black band beyond (see image below). Adult males measure 26-38 millimeters while females are 32-45 millimeters.

The Blue-legged Grasshopper ranges from the southern reaches of the prairie provinces in Canada to Oklahoma and northern Texas, west to Arizona, Utah, and eastern Idaho. This species is at home in a variety of grassland habitats, from shortgrass prairie like we have here in Colorado to wet meadows at higher elevations. The adults are present from June or July to September.

The first specimen I encountered was on the Fourth of July this year, where it was sitting on the sidewalk barely a block away from my residence in east Colorado Springs. I thought the red and blue colors were quite appropriate for the holiday. I caught the insect and brought it home for better images under controlled conditions, where I could spread the hind wing, too.

The second one I found in a degraded shortgrass prairie at the top of the hill above our neighborhood. So far these are the only two I have seen and I wonder if this is simply not an abundant species. Apparently it is closely tied to its favorite foodplant, Western Wheatgrass, so maybe I should be looking in juice bars and smoothie shops.

It feeds in a very strange manner. The adult grasshopper scales the stem of its target, then snips off a three- or four-inch terminal section of leaf and lets it fall to the ground. The grasshopper then descends to the ground and, manipulating the grassblade with its front legs, eats it from one end to the other.

It is likely that this species is capable of fairly long migrations given its long wings and aerodynamic shape, but more research is needed to learn whether such flights are a regular aspect of its behavior.

Metator pardalinus goes through five nymphal instars before reaching adulthood. Both older nymphs and adults can be gregarious, as recorded in some Montana populations.

A tangle-veined fly, but not Trichopsidea clausa

An interesting enemy of the Blue-legged Grasshopper is Trichopsidea clausa, a species of tangle-veined fly in the family Nemestrinidae. Tangle-veined flies resemble large bee flies in appearance. The adult female fly lays thousands of eggs on elevated objects such as towering weeds or fenceposts. The tiny larvae that hatch are thought to be blown randomly across the landscape. When (or if) they contact a grasshopper, they quickly penetrate the body wall of the host and then live as an endoparasite. Up to 80% of female Bluelegged Grasshoppers have been recorded to be parasitized in some years, and since the fly larvae consume the eggs and soft tissues, the grasshoppers cannot reproduce. The grasshopper sometimes wins, though, sealing off the tiny (0.5 mm) fly larva when it first enters its body.

Sources: Capinera, John, L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca, New York: Comstock Publishing Associates (Cornell University Press). 249 pp.
Helfer, Jacques R. 1972. How to Know the Grasshoppers, Cockroaches, and Their Allies (2nd edition). Dubuque, Iowa: Wm. C. Brown Company Publishers. 359 pp.
Pfadt, Robert E. 1994. "Bluelegged Grasshopper," Wyoming Agricultural Experiment Station Bulletin 912
"Section I: Biological Control," Grasshoppers: Their Biology, Identification, and Management. USDA (information on the tangle-veined flies).

4 comments:

  1. I assume, then, that Trichopsidea clausa parasitizes any species of grasshopper? With its random method of dispersal, does it parasitize just grasshoppers or any insect that it contacts in its tiny larval stage? How long do its larvae remain viable if they don't encounter a host quickly?

    Cynthia, aka Gaia gardener

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    1. Excellent point, Cynthia, and good question, too. The online paper I read said the larvae can survive up to 14 days. That is quite incredible for such a tiny, vulnerable maggot.

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  2. Thanks, Eric, for answering. Fourteen days without food is actually pretty amazing for such a tiny animal....

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    1. You're welcome; and, I agree, it *is* amazing!

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