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Bob Howe

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This Northern bush katydid, Scudderia septentrionalis occurs in the northern 2/3 of the US and southernmost Ontario and Quebec. Even though it has a wide distribution it is not usually seen, because it spends most of its time high in the tree canopy, especially in oak woods. People most often encounter the males at night because they are attracted to lights.

The song is a raspy series of "ticks". It consists of six or more sharp ticks followed by 6-8 notes that sound like "dee-dee-dee, the notes last about 3 seconds and increase in volume toward the end of the song. S. scudderia only sings at night and like all katydids, only the males produce songs in order to attract females.

Katydids are in the family Tettigonidae and are different from other insects in the order Orthoptera (Grasshoppers, crickets, and katydids). Identifying features of katydids include long thin antennae, tarsae composed of 4 segments, and a tympanum (hearing organ) that is located at the base of the front tibia. Female katydids have a long scimitar shaped ovipositor that is used to lay eggs . The ovipositor is visible in the photo above just under the wings and to the right of the pink spine-like cercus. Katydids use their cerci like secondary antennae.

All Katydids are herbivores and eat seeds, flowers, fruits and leaves. Most species are not very selective and will eat a variety of plant species. There are about 250 species of katydids in the United States.

Katydid males make their song by scraping their forewings together. They raise their first pair of wings (tegmina) so that the toothed file on the underside of the left tegmen (which is on top of the right tegmen) is rubbed against a raised vein (scraper) along the edge of the right tegmen near its base. This is called stridulation. The actual notes of the song are determined by the distances between the teeth and by how rapidly the toothed wing vibrates. Just this year scientists Montealegre and Mason from the University of Toronto used high speed video electron micrographs to examine the teeth and noticed that the distance between the teeth increases along the edge. That means the katydid has to pull faster toward the end of the file in order to produce a pure tone.

Other studies have shown that amplitude (loudness) is the most important thing that female katydids focus on. The louder the call the better. Katydids listen using hearing organs (tympanum) located on their front legs. Not only do they listen for the calls of other katydids, but research shows that they can use their tympanum to listen for bats one of their major predators.

More information about Katydids:

Keys and Guides

References

  • Johannes Schul and Adam C. Patterson (2003) What determines the tuning of hearing organs and the frequency of calls? A comparative study in the katydid genus Neoconocephalus (Orthoptera, Tettigoniidae) The Journal of Experimental Biology 206, 141-152
  • Montealegre-Z, F. and Mason, A. C. (2005). The mechanics of sound production in Panacanthus pallicornis (Orthoptera: Tettigoniidae: Conocephalinae): the stridulatory motor patterns. J. Exp. Biol. 208,1219 -1237.

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Last updated on May 9, 2014