Wednesday, August 1, 2012

Ceratopsyche bronta and Ceratopsyche morosa: More Netspinner Identifications

So the rule is: when you find a common netspinner that appears to be Hydropsyche in terms of the genus (key features: 1) forked fore trochantin, and 2) two large sclerites posterior to the prosternal plate) and you wish to ID it to the level of species, be sure to check the descriptions for:

1) Ceratopsyche larvae in Steven Beaty's "The Trichoptera of North Carolina," pp. 72-73
2) Symphitopsyche larvae in Guenter A. Schuster and David A. Etnier, "A Manual for the Identification of the Larvae of the Caddisfly Genera Hydropsyche pictet and Symphitopsyche ulmer in Eastern and Central North America," pp. 1-60 (published in 1978).  (Be sure to look at p. 25 for excellent drawings of common larval head patterns.)

Both sources are available online.  Symphitopsyche is apparently no longer used as a Hydropsychidae genus name, and remember that what some entomologists call Ceratopsyche others ID as a "type" of Hydropsyche.  As an amateur, this disagreement appears to me to be a matter of "splitting hairs" -- which it actually is!  (See the previous entry.)

Using those sources, I have now identified two additional common netspinners that I have found in our streams.  In fact both of these were found in the Moormans River in Sugar Hollow.

1. Ceratopsyche bronta, or, if you prefer, Hydropsyche bronta.  This is the larva pictured at the top of the page.  In that photo, you can see all that you need to see for this species ID.  Quoting from Beaty: "...head with 3 distinct transverse stripes with cental stripe expanded mesally and often with light spot in middle; nota with anterior and posterior transverse dark bands." (p. 73)  The head pattern is definitive, though the "light spot" in the middle band may or may not be present (Schuster and Etnier, p.39).  Our larva does have the light spot:

And there are clearly dark anterior and posterior bands on the pronotum, mesonotum, and metanotum.

2. Ceratopsyche morosa, or, Hydropsyche morosa.  Pictured below.

Again, the head pattern is definitive for the species.  From Beaty: "...head with 5-6 pale spots in checkerboard pattern on frontoclypeus (top of head) and usually with three small white spots at posterior angle of frontoclypeus."  Here is a close-up of the top of the head.

Perfect.  He adds another feature that we can see if we turn over the larva and look at the "chin": "...stridulatory areas [the striations that the larva rubs to make a "warning" noise ] on venter of head darkly pigmented."  Sure enough.

(For Schuster and Etnier's more detailed species description (their S. morosa), see pp. 41-43 in the "Manual.")  Both of these netspinners, by the way, are fairly intolerant: both have a TV of 2.3.

If you find the right sources to use, once impossible tasks can become fairly easy.  Below: ventral views of C. bronta and C. morosa.

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