Generals on the March

Horse Lubber Grasshopper

Horse Lubber Grasshopper © Sheri Williamson

Generals on the March by Tom Wood and Sheri Williamson

A generous late summer “monsoon” season in the desert grasslands of the Southwest translates to a fall population boom for many wildlife species. Some of the “boomers” are easier to see than others, including the gigantic grasshoppers known as Horse Lubbers. They’re one of the two largest grasshoppers in North America (the other being the Eastern Lubber). A mature female may be 2.75 inches in length and weigh as much as three male Black-chinned Hummingbirds!

Many of our human neighbors here in southeastern Arizona know the Horse Lubber as the “Mexican General,” a colloquial name inspired by its bold pattern of bright yellow accents on a background of black and dark green, like a high-ranking officer in full dress uniform. Grasshoppers often have colorful hindwings, and a few are quite colorful on close inspection (the Rainbow Grasshopper, for example), but no other grasshopper in the Southwest is as in-your-face conspicuous as the Horse Lubber.

Like many desert insects, Horse Lubbers depend on the short-term abundance of food resulting from the late summer rains. When “monsoon” thunderstorms transform the desert into a virtual all-you-can-eat salad bar, lubber nymphs hatch from eggs laid the previous year and begin to gorge themselves. As they reduce the food supply in one area, they march on to greener pastures, passing through several instars (growth stages) as they go. Early instars are chunky and wingless. By the final stage, they have slimmed down and grown wings for greater mobility.

The lubber boom might seem to be a boon for predators, but it pays to be suspicious about a critter that’s abundant, conspicuous, and easy to catch. You’ve probably already figured out that the gaudy attire and sluggish behavior of Horse Lubbers are aposematic, a warning to potential predators of well-armed prey. Like Monarchs and Pipevine Swallowtails, the big ‘hoppers are infused with toxic chemicals that make them unpalatable, but making a predator nauseous is a Pyrrhic victory. The preferred outcome is not to get eaten in the first place. Threatened lubbers start by hissing and flashing their bright salmon-red hindwings. If that doesn’t work, they’ll spray their attackers with noxious chemicals, like six-legged skunks. It doesn’t take too many such encounters for predators to learn not to mess with lubbers. Our pet chickens enthusiastically chase after any small, cryptically colored grasshoppers that find their way into our yard, but they give the big black ones a wide berth.

We think of grasshoppers as herbivores, but Horse Lubbers like a little meat in their diet. They’re not fussy; carrion is fine fare, and they’re not above cannibalism. As with skunks, the sluggish and fearless behavior of lubbers makes them vulnerable to traffic. Those that don’t make it across the highway may become “road food” for their traveling companions. In fact, their chemical defenses are so successful that about the only animal that can stand to eat a Horse Lubber is another Horse Lubber. As our collegue Pete Corradino discovered, Loggerhead Shrikes in Florida will eat Eastern Lubbers after letting them “mellow” a bit to break down the toxins, but we haven’t observed this behavior in Arizona. Maybe Horse Lubbers are “spicier” than their southeastern cousins?

Sheri and Tom (Southwest)

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