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Southern Oregon Fishfly - Orohermes crepusculus

Southern Oregon Fishfly - Orohermes crepusculus
Chinquapin Group Campground, 12 miles east of Cave Junction, western Siskiyou Mountains, Josephine County, Oregon, USA
July 7, 2015
Size: Approx. 5-6 cm
[For full-size image, click here...then click the resulting image in your browser window once more.]

This megalopteran was spotted just before dark (i.e. "crepuscular" activity!) at the edge of a large grassy campground area (~1860' elevation) separated from Grayback Creek (good larval habitat) by a narrow wooded corridor. The area was within surrounding mixed hardwood and coniferous forest. It was difficult to photograph the fishfly due to the low light and, mainly, its active fluttering about. The distal 2/3's of its right antennae had apparently been broken off.

Since the location is not far north of the California border, I initially used the keys in the Megaloptera chapter (written by H. P. Chandler) in Usinger's 1956 "Aquatic Insects of California". The large wing expanse (= wing-tip to wing-tip length) indicated this was in family Corydalidae, and wing characters (lack of white spots & radial sector with 4 forks) led to genus Dysmicohermes in Chandler's treatment, and thence to D. crepusculus (later moved to genus Orohermes by Evans in 1972(1), cf. Evans 1984). Earlier, I had considered D. disjunctus a good candidate here...but that species has much larger overall size; denser long-wooly vestiture on the thorax; and wing venation (posterior branch of medial vein "M" forked) that are all at odds with this specimen...which convinced me this is not D. disjunctus.

On the other hand, the original description of D. crepusculus on pg. 107 of Chandler (1954) fits very well here...except the intact antenna here has 42 segments (see 2nd image of series) rather than the 35 of the male holotype described by Chandler, and the segments are less than 3 times as long as wide. But I believe this is a female (see 6th image in series), and perhaps these antennal characters are sexually dimorphic (females are generally larger) and/or somewhat variable? Chandler describes the male holotype of D. ingens as having 52 segments, and that species is very similar to D. disjunctus (the latter ranges into Oregon, whereas D. ingens is known only from the Sierra Nevada). Recall that individuals of D. disjunctus are much larger than the specimen here. So I'm assuming the number of antennal segments can be somewhat variable, and the 42 of my putative female here is closer in number to the 35 described for the male holotype of D. crepusculus than the 52 desribed for the male holotype of D. disjunctus. The wing venation diagrams for these two species from pg. 109 of Chandler (1954) appear in the collage posted as the 4th image in this series. There are (relatively minor?) discrepancies between the venation patterns in the diagrams for both those species vis-a-vis my individual here...but overall the agreement is better with Orohermes (=Dysmicohermes) crepusculus.

As a double-check, the wing venation and thoracic vestiture characters visible in my photos are sufficient to work through Norm Penny's 1999 key to world genera of the subfamily Chauliodinae and arrive clearly at the (monotypic) genus Orohermes, so I'm confident of that ID here. The lack of long wooly hair on the thorax, and the relatively wide costal margin (somewhat flaring proximally) are relatively conspicuous "quick" gestalt characters for Orohermes. Details of the salient wing venation characters appear in the remarks under the 3rd -- 5th images in this series.

As always...enlightening comments, insights, correction, and/or confirmation are welcome and appreciated!

Images of this individual: tag all
Southern Oregon Fishfly - Orohermes crepusculus Southern Oregon Fishfly - Orohermes crepusculus Southern Oregon Fishfly - Orohermes crepusculus Southern Oregon Fishfly - Orohermes crepusculus Southern Oregon Fishfly - Orohermes crepusculus Southern Oregon Fishfly - Orohermes crepusculus Southern Oregon Fishfly - Orohermes crepusculus