Two-spotted Tree Cricket

August 17, 2009 at 6:24 am (methods, singing insects)
Tags: Davis's tree cricket, narrow-winged tree cricket, Neoxabea bipunctata, Oecanthus exclamationis, Oecanthus niveus, Springbrook Prairie, Timber Ridge, two-spotted tree cricket

by Carl Strang

One of the goals in my singing insects study this year is to sort out the songs of three arboreal tree crickets. In the field I have found that their songs are not as distinct from one another as reference recordings and descriptions seemed to suggest. Two of the three species I have seen, and so confirmed their presence in DuPage County. Today I begin with what I suspect may be the only one singing as early in the season as late July and early August: the two-spotted tree cricket.

This photo shows a female, with the two large spots on her back that give the species its name (males lack them, and are pale). She sits on the arm of one of the 2006 Roger Raccoon Club  kids, who brought her to me for identification. Until two weeks ago, she was the only one I had seen. Certainly the references were correct in saying these are not easy to find. They live in trees, often well above the ground. The male’s song, which you can find here  or here, is a strained, often dissonant sounding trill that is interrupted fairly frequently by brief pauses that often are filled with stuttering sounds. Unfortunately, the same description applies more or less to the songs of Davis’s tree cricket and the narrow-winged tree cricket, though the tone of the last seems more melodic to my ear.

Two-spotteds begin to sing at dusk. On August 6 I was at Timber Ridge Forest Preserve, strolling the Great Western Trail with ears open for insect songs, when scattered tree crickets in this target group began to sing. All had identical songs, but one in particular seemed to be closer to the ground and just off the trail. After a short time I found him.

He was on the underside of a big grape leaf. Here he is close up.

He was using a trick for which some of the tree crickets are known. He had chewed a circular hole in the leaf, and was using it to amplify and possibly direct his song (tree crickets sing by elevating their wings and vibrating them against one another).

I made a recording, then prepared to collect him for identification. But when I put my flashlight on him again I found this was unnecessary.

A female had arrived on the scene, and there was no mistaking her identity. The male kept his wings elevated, and continued to vibrate them occasionally in song. She was palpating her way slowly up his back in search, I believe, of secretions that some of the tree cricket males provide as nuptial food gifts in a prelude to mating.

The next evening at dusk I was at Springbrook Prairie Forest Preserve. I heard the same song coming from near the top of a 15-foot-tall bur oak beside the trail. Looking up toward the point from which the sound seemed to be coming, I noticed that one of the leaves had a circular hole in the middle. When I illuminated it with my flashlight, sure enough, there was another male two-spotted tree cricket. So, at least with plants having relatively large leaves, I now know to look for distinctive circular holes that may help me to find these elusive insects.