Black-horned Subtleties

by Carl Strang

Lately most of the members of the nigricornis group of tree crickets I have been catching at Mayslake Forest Preserve have proved to be prairie tree crickets. Last week I found an exception that brought out some of the subtle distinctions among these insects.

The broad black band on the underside of the abdomen narrowed this one down to being either a black-horned or a Forbes’s tree cricket.

The tips of the legs and antennae likewise were black. However, he was pale on top.

There was a diffuse darker stripe down the top of the head and pronotum, but so pale as to be ambiguous.

With this group of species it is a good idea always to look at the antenna spots. In this one the spots on the basal segment were large, fused and fairly well defined.

The spots on the second segment were very narrow, however, and well separated, as they should be in this species pair.

Another lesson I learned from this cricket was the importance of viewing angle on those second-segment spots. You need to look straight down on the inner spot with respect to its own position, rather than from the cricket’s mid-line, which gives only a slightly tangential view of the critical spot. After taking the photos I took the cricket home and he sang for me, so later the recording should allow me to determine which of the two sibling species he was.

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