Members of the insect order Orthoptera — grasshoppers, crickets, and katydids — can be found year-round on Martha’s Vineyard (immatures of a few species overwinter, and can be found on mild winter days). But the peak season for these insects is squarely the late summer, with the third week of July usually featuring a surge of orthopteran activity as many species reach maturity all at once.
Among the more than 50 Vineyard species of orthoptera, the most mysterious and arguably the most interesting are our eight tree cricket species, members of two genera in the subfamily oecanthinae. One of those species is a bit suspect: Known here only from a single record in an agricultural setting, the broad-winged tree cricket (Oecanthus latipennis) may have occurred here as a one-off, accidental import, instead of as an actual native population. Two of the remaining species, Davis’s tree cricket (O. exclamationis) and snowy tree cricket (O. fultoni) are scarce (though perhaps overlooked), with just a few documented Vineyard occurrences.
But the remaining five species are at least locally common. O. nigricornis, the black-horned tree cricket, is mostly confined to shrub swamp along the edges of the Island’s great ponds, where this cricket can be plentiful. The four-spotted tree cricket, O. quadripunctatus, is very common in dry settings that mix grasses and forbs. And the fairly common pine tree cricket, O. pini, is as its name suggests a close associate of pines, especially pitch pine in the case of the Vineyard.
The final two, the narrow-winged tree cricket (O. niveus) and the two-spotted tree cricket (Neoxabea bipunctata), are downright abundant, found in both natural and human-modified habitats of many kinds, including yards and even downtown areas. Whether you know it or not, you’ve undoubtedly heard the calls of at least these last two species. And if you get out much, you’ve heard some of the others, as well.
Tree cricket calls, produced when males rub specially roughened sections of their wings together, are central to the lives of these unusual insects. Males of most of our species call both day and night, and in many cases, they call almost continuously. These songs, aimed at attracting females, are all essentially trills — vibrations on a single pitch — and the song of each species is distinctive. In some cases, the trills are short, perhaps better thought of as chirps than trills; in other cases, trills are broken up by brief silences into a series of short bursts lasting a few seconds; and the calls of a couple of species go on and on for minutes at a time. With a little practice,one can learn to recognize the patterns and tone qualities of the calls, making it possible to tell what tree crickets are around.
Seeing these insects is another matter entirely. Tree crickets, a bit under a inch long on average, have elongated bodies, and slender, spindly legs. Combine that build with protective, greenish coloration and a talent for concealment, and you’ve got an insect that is very, very hard to spot. If you’re slow and careful, it is sometimes possible to find a tree cricket by zeroing in on an ardently calling male. And most of our species show at least some inclination to visit lights at night, whether porch lights or the specialized lights moth enthusiasts set up to attract nocturnal insects. But I’d say I hear 50 tree crickets for every one I actually get a look at.
Tree cricket eggs, laid on or in the stems of vegetation, overwinter and then hatch in late spring. The tiny nymphs that emerge, already showing the characteristic body shape of this subfamily, feed on vegetation, and grow through a series of five molts until they reach maturity. About their reproductive habits, I have room only to say that tree cricket mating procedures rank among the most bizarre bits of natural history I’ve ever encountered.
Intrigued by tree crickets? Well, you’re in luck! The program I run for BiodiversityWorks, called the Martha’s Vineyard Atlas of Life, is sponsoring a webinar on these amazing insects. It will be held Thursday evening, July 27, from 7 to 8 pm, and features Nancy Collins, who is in my view the leading tree cricket expert in North America. Her website, oecanthinae.com, pulls together information on tree cricket identification, calls, ecology, behavior, reproduction, and more. Nancy’s presentation will include the highlights from that site, with a Vineyard spin.
The webinar is free, but we ask participants to preregister as a measure to reduce the risk of internet trolls. Simply complete the form at this link: bit.ly/AtlasTreeCrickets. A few days before the presentation, you’ll receive an email with a Zoom link for the webinar. This is a rare chance to learn about unusual insects from an engaging and profoundly knowledgeable expert.
In the meantime, keep an ear and an eye open for the start of the Island’s tree cricket season!