In my personal collection of Orthoptera, there is a row of grasshoppers with radically different wing colors. Most have bright orange wings. A few bear pale yellow wings. One has a lovely rosy red shade. Yet if you examined the determination labels on all those specimens, you’d find that they are all identified as one species: Psinidia fenestralis. What gives? The answer has to do with individual variation as well as geographic location.
Psinidia is a small band-winged grasshopper, less than half the length of the common Carolina (or black-winged) grasshopper Dissosteira carolina. It is widespread in the eastern U.S, but is also fairly habitat-restricted, preferring to live in small open patches of sand within grassy areas. It has a distinctive ‘bug-eyed’ appearance along with very long, somewhat thickened, antennae. The body pattern is extremely variable, but usually perfectly matching the appearance of the sand on which it lives. Adults are usually present from July to October, and in Florida they are out year-round. When disturbed, they do not fly far, making short, fast flights that often circle back to the same area of sand. I have discovered several populations of this grasshopper up and down the east coast. In almost every population, the hind wing coloration has been different. In part this is due to individual variation – ‘normal’ populations of the species have bright orange hind wings, but occasional populations have rosy red wings. In Florida, where there is sandy habitat almost everywhere, it seems as though orange-winged individuals prevail, judging from BugGuide records. My single specimen from Florida had orange wings, but a population I found in a small isolated sand pit in Maryland consisted solely of rosy red-winged specimens.
In the New England states, an interesting phenomenon occurs. Populations with yellow wings become more prevalent as one travels up the coast, with yellow-winged individuals eventually becoming dominant in Maine. I am not sure as to why this is, but the northeastern populations tend to be very localized and quite far away from other populations. As such, there probably isn’t a lot (perhaps not at all?) of interbreeding. Compounded by this is the fact, mentioned earlier, that Psinidia doesn’t like to leave its sandy habitat, and would be highly unlikely to travel long distances across unsuitable habitat like forests, swamps, or urbanized places. This means that these isolated populations are free to develop without influence from other populations, and simply because of random genetic drift, an odd wing color variant might become the dominant one. This still doesn’t explain why yellow wings totally dominate in Maine, though. Perhaps somehow it is advantageous in more northern locales? Or is there some other selective agent at work? More study is needed for sure. In any case, I have located 6 Psinidia populations in Maine, New Hampshire, and Massachustts (2 per state!), and there is a clear line of transition. Both Maine populations, the more northerly New Hampshire population, and one of the Massachusetts populations all have yellow wings, and are all in very small, restricted places. The other Massachusetts population was quite large and in an extensive sandy area, and all individuals bore orange wings. The southern New Hampshire population is particularly compelling – most of the Psinidia here had yellow wings, but a few boasted pale orange wings! Clearly there is something going on here of interest. I am hoping to locate more Psinidia populations of the northeast in the future to get a clearer picture of what is happening.