Tetrigidae: Tetrix vs Paratettix
The family Tetrigidae of pygmy grasshoppers has been relatively neglected in the party of taxonomy. This has led to several contradictions in identification and much confusion. I have noticed a lot of requests for keys, which are lacking, most of which are outdated, and contain confusing terminology that may bore those interested in this group. In addition, some checklists involve species with no accessible records of occurrence in the covered region(s) and contradictory/outdated generic and specific placements. Now fortunately this group appears to have been treated much better and more recently outside of North America. The most recent, useful source in tetrigid taxonomy for North America, specifically Canada, was a 1985 article in the Government of Canada's The Insects and Arachnids of Canada series, authored by Vickery and Kevan titled "The grasshoppers, crickets and related insects of Canada and adjacent regions : Ulonata: Dermaptera, Cheleutoptera, Notoptera, Dictuoptera, Grylloptera, and Orthoptera". Obviously, this publication does not cover the numerous additional tropical genera and species of tetrigids found further south.
In this journal post, I'm starting rather simple, with the separation of the genera Paratettix and Tetrix. Firstly, the family Tetrigidae can be characterized by the pronotum or thorax being extended backward into a point, with this point looking like the end of pairs of wings but are actually not; the wings/tegmina if present consist of a usually darker, more rigid membranous mass visible just under the end point of the pronotum. Thus the pronotum often covers the wings entirely.
Paratettix and Tetrix are similar to each other and also probably the most common along with Tettigidea, which has less protruding eyes, a pronotum that covers a little bit of the neck giving a hooded appearance, and looks more like an acridid grasshopper in build.
Differences between Tetrix and Paratettix:
In Tetrix, the fastigium in dorsal view or top of the head is noticeably wider than the width of a single eye in the same plane.
http://orthoptera.speciesfile.org/Common/editImgSnd/GetThumb.aspx?ImageID=111378&Width=640In Paratettix, the fastigium in dorsal view is more variable in width.
http://orthoptera.speciesfile.org/Common/editImgSnd/GetThumb.aspx?ImageID=111251&Width=640
http://orthoptera.speciesfile.org/Common/editImgSnd/GetThumb.aspx?ImageID=111250&Width=640In Tetrix, the fastigium in lateral view advances forward enough between the eyes to a distance noticeably past the eyes.
http://orthoptera.speciesfile.org/Common/editImgSnd/GetThumb.aspx?ImageID=151364&Width=640In Paratettix, the fastigium in lateral view advances forward between the eyes to a distance not noticeably past the eyes.
http://orthoptera.speciesfile.org/Common/editImgSnd/GetThumb.aspx?ImageID=111255&Width=640- In Tetrix, the head appears to be more flatter on top and straight-margined than Paratettix.
- The middle femora of Paratettix can be lobed underneath (the lower margin wavy) but is often less the case in Tetrix.
In the future, the Nearctic species of Tetrix may be delineated, but Paratettix is more problematic to identify to species. I may also form a more photographic and comprehensive guide to tetrigid fauna.
