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B. Understanding Cicadas (Continued)

7. Classification

Abstract

The northern cicadas belong to three monophyletic subfamilies: Cicadinae, Cicadettinae and Tibicininae , with 45 species of cicadas reported from Canada and adjacent USA. Five of these Magicicada septendecula (Section 10C), Okanagana annulata (Section 10H), O. luteobasalis (Section 10H), Tibicen dealbatus (Section 10D), and T. robinsonianus (Section 10D-1) are possibly hybrids where closely related cicadas occupy the same territory. The large genus Tibicen is subdivided into the great harvestflies, true Tibicen, and the lesser harvestflies, tentatively associated with Cryptotympana. The species formerly known as T. marginalis (or T. walkeri) is corrected to T. pronotalis. Traditional characters for identification of the difficult genus Okanagana are supplemented by data from the meron (a lobe on the outer edge of the coxa) of the hind leg, and form of the theca.

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Drawing of the three subfamilies of cicadas: Cicadinae, Cicadettinae, Tibicininae

Although cicadas are generally thought to be well-known, and have been studied extensively over many years, there still remains a disquieting amount of unreliable and partial taxonomic information. Modern techniques such as sonograms, morphometrics, dissections (Section 6D) and genetic analysis should yield a bountiful harvest of additional information. The amateur can also play a major role. Photographs of living insects and information on life histories are badly needed. This is particularly acute when songs are in question. For example, of the 40 species reported here (see Northern cicada species (Section 10), the songs of only 18 have been reported, and the accounts are not always in agreement. Some of the differing accounts may indicate "sibling" species that are hard to distinguish, but others may be merely a matter of "ear"; some people hear things in a different way than others do. Some reports are probably misassociations of song and cicada species where two or more cicada species are found together. Still others are the result of distance from the source, or other factors such as temperature or the age of the individual cicada. An example is a New Jersey record of the Dog-day Cicada song as "high pitched and shrill, but not very loud".

There is also a great need for a new "higher" (suprageneric) classification of world cicadas. For this, and for genera of cicadas outside our northern fauna, see World Genera (Section 8).

The traditional classification Footnote 1 was based on a single feature: whether the tymbals were concealed (Cicadinae), or fully exposed (Tibicininae), and an intermediate condition (Gaeninae) was included. This classification placed the very different Tettigarctidae as a mere subset of Tibicininae. Subsequent workers further confused the situation by elevating Cicadinae to family rank, and dividing it into two subfamilies, the name of one of which (Tibiceninae) differs from the most primitive group (variously a subfamily or family) by only a single letter!

The first important step in producing a classification that more nearly reflects lines of descent (phylogeny) was taken by excluding the "hairy cicadas Footnote 2 ( Tettigarctidae ) from the Cicadidae. This reclassification recognized the very different morphology of hairy cicadas (concealed thorax between the wings; large hind wings; tiny tymbals; no tympana, opercula or resonating chambers in the abdomen) and their unique biology. Unlike other cicadas, which revel in bright sunlight and the heat of the day, hairy cicadas hide during the day, coming out only at dusk, and are active even in cold weather Footnote 3.

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A 'hairy' cicada - Tettigarcta

A modern classification of the northern Cicadidae should include three "natural" (monophyletic) subfamilies Footnote 4:

  1. Cicadinae [including Tibicenini: Diceroprocta (Section 10E), Neocicada (Section 10G), and Tibicen (Section 10D) are advanced cicadas with very large male opercula (but very small ones in the female), tymbals more or less concealed, and the male terminal segment closed by a vertical uncus enclosing a tubular theca. This subfamily includes the smallest cicadas in North America (Beameria, a southern genus of Fidicini) as well as the largest (Tibicen).

  2. Tibicininae including Platypediini: Okanagana (Section 10H) and Platypedia (Section 10F) are primitive cicadas with the opercula small in both sexes and tymbals exposed, but with the male terminal segment distinctively modified, closed by a long, horizontal uncus clasping the slender, highly flexible theca in a spine-edged groove on its inner face.

  3. Cicadettinae Cicadetta (Section 10J), and Magicicada (Section 10C) are cicadas with an unusually large number of spines on the front leg (most cicadas have only two), and other characters intermediate between Tibicininae and Cicadinae: male opercula larger than those of the female, tymbals exposed, and the male terminal segment open, exposing a tubular theca.

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