Wild Side : The grasshoppers, crickets, and katydids of Martha's Vineyard
Photo by Matt Pelikan
Regular readers may have noted that I suffer from a growing interest in Orthoptera – that is, in the insect order that includes grasshoppers, crickets, and katydids. The affliction began four or five years ago, when I noticed that tiny green grasshoppers were among the first insects to become active in the spring, leaping around in sunny spots in my garden and against the house foundation, as early as late February. I was intrigued, and finally, this year I've made a modest beginning at studying these interesting and ecologically important insects on the Vineyard.
I'm fairly well equipped to begin such a study. Having spent lots of time learning about butterflies and dragonflies, I've already got a handle on some key aspects of insect taxonomy and anatomy. Though I haven't had much formal training, I do have some experience with using scientific keys to identify things, and with collecting and examining specimens under magnification (necessary for positive ID of many insects). I'm fairly good at photographing small animals for later identification, and best of all, there are excellent resources in published form and on the web to help with insect ID.
Still, starting to study a new subject always leads to a certain amount of frustration. In the case of learning about a new group of animals, one major barrier to learning to distinguish one species from another is that you don't know what characteristics matter for identification. You'll intensively study some critter, noting what you feel sure must be diagnostic field marks. But when you consult an identification guide, you often find that dozens of species display those field marks, and what you so carefully noted isn't helpful for putting a name to the beast. So your first few attempts at identification are always tentative and usually wrong.
On the other hand, the early stage of learning about something can be exhilarating. You're on the steep part of the learning curve, and every day can bring a sense of meaningful progress. Each new species you become familiar with gives you another point of comparison, and the initial sense of utter confusion quickly gives way to a dawning sense of understanding. The various sub-groups (meadow katydids, false katydids, predacious katydids, etc.) start to seem meaningful and distinctive, and you start to get a feel for where and when to look for your quarry.
So far this year I've managed to get acquainted with about 20 species of Orthoptera — photographing them, collecting them, or studying them carefully in the field. This may be a third or so of the total number present on the Vineyard, but it will provide a good base for more refined searching next year. Within a few years after that, I'd hope to have assembled a reasonably good checklist of Vineyard Orthoptera, and to have a good working knowledge of where and when to find most of our species. Hopefully, I will have learned to recognize the calls of our crickets and katydids; the distinctive noises they make by scraping body parts together help the insects communicate and furnish the observer with a powerful identification tool.
One conclusion, already, is that a relatively small number of species account for the vast majority of individual Orthopterans. Medium in size, the northern green-striped grasshopper is abundant and widespread on the Vineyard in spring and early summer. In July, the Carolina grasshopper becomes common and conspicuous, a large grasshopper (probably the Island's largest) that flies strongly on black-and-yellow wings. And now, in the late season, the red-legged grasshopper is turning up nearly everywhere. As far as I know, if you see a grasshopper on the Vineyard, odds are good it belongs to one of these three species.
Such a pattern of abundance is not surprising; for most kinds of animals, a small portion of the total diversity dominates. But I'm impressed by the sheer numbers of these grasshoppers, now that I'm looking for them. By virtue of their numbers, they must surely be of considerable ecological importance, as prey for birds or other insects and as herbivores that presumably chew some kinds of plants a lot more than others.
The dominance of a few species doesn't in the least mean that our Orthopteran diversity is low. As I start to learn the most common species, I'm getting better at noticing grasshoppers that don't belong to a species I recognize. And I'm learning that the less common species truly are out there, often turning up serendipitously: a two-spotted tree-cricket joined a dinner party on our deck one night, for example, and a protean shieldback (what a great name!) turned up in a black-light trap I had set overnight for moths.
Overall, I'd say that my initial spark of interest in these insects was well founded. These insects have proven diverse, abundant, and widespread on the Vineyard, and fascinating in their appearance and behavior. True, every answer I find raises many more questions. But that just makes the learning process more interesting.
I'm already looking forward to next year.