by Joseph DeSisto
The desert is a busy place, both for animals and for biologists. Before we entered Coronado National Forest in southeastern Arizona, I stepped out of the car to look around, and see what surprises were waiting for me on the roadside. First was a whiptail lizard. I actually saw several, but only one was slow enough for me to photograph:
There are 11 species of whiptail lizard in Arizona alone, and many more throughout the Americas. They are insectivores, fast hunters that skate over the sand to chase down their arthropod prey. Whiptails aren’t very choosy — desert animals seldom are — but one insect they avoid was also at the roadside: the rainbow or “barberpole” grasshopper.
The grasshoppers, too, were wary of me and my camera but their wariness was half-hearted — most predators, including whiptails, know to steer well clear of the barberpole’s spectacular warning colors. The colors are a powerful advertisement that this insect is highly toxic and makes for a poor meal. Experiments have shown that whiptails will even avoid non-toxic grasshoppers if they have been painted with the barberpole’s colors (McGovern et al. 1984).
This grasshopper doesn’t have fully-developed wings, and can’t fly. When I first began observing them, I assumed the pads above the legs would develop into flight-ready wings when the hoppers reached maturity. This is the case with most grasshoppers and many other insects — wings only appear at adulthood.
But then I saw two individuals mating, without wings:
So the wingless grasshoppers are in fact adults. Most grasshoppers use their wings to fly away from danger, but the barberpole’s defense is so effective that the ability to fly has become redundant. Wings take a lot of energy to develop, so over time, as the grasshoppers stopped using them, the wings were reduced until they became little more than blue-and-white pads. The wing pads they have now are vestigial, like the hipbones of a whale, a reminder of their evolutionary past.
McGovern G.M., J.C. Mitchell, and C.B. Knisley. Field experiments on prey selection by the whiptail lizard, Cnemidophorus inornatus, in Arizona. Journal of Herpetology 18(3): 347-349.