Boreus coloradensis  Byers, 1955


Diagnosis:  Body dark brown to black; length, male, pinned: 2.5 – 3.0 mm; female, pinned: 4.5 – 5.0 mm.; male, in alcohol: 3.2 – 4.9 mm; female, in alcohol: 4.3 – 5.4 mm.  Ratio of length of maxilla-labial complex to rostrum = 0.86.  No bristles on pro-, meso-, and metanota.  Legs lack apical femoral spine.  Male forewings abruptly narrowed at mid-length, with 19-22 mesal spines and 8 to 13 lateral spines.  No spines on hindwing.  Female forewing oval, covering hindwing.  Male 8th tergum and sternum fused; 9th tergum and sternum not fused; 9th sternum evenly rounded at apex.  Tergal hood of 9th tergum about half the width of tergum, with a medial, longitudinal ridge.  Female ovipositor long, ninth sternite slightly more than twice height of eighth segment.


Distribution – Geographical:  Adults of this species have been collected from the front range of the Rocky Mountains of Colorado and northern New Mexico and the montane, sagebrush meadows of eastern Wyoming (Byers & Shaw, 2000) west to Nevada, Utah, and western Montana.


Distribution – Temporal: 1 October until 25 May at elevations of 7,000 ft. to 12,000 ft. (2135 m – 3050 m) in the Rockies and 4700 ft. to 6550 ft. (1434 m – 1998 m) in Utah.


Ecology:  This species has been found in the rich mosses bordering Blacksmith Fork near Logan, Utah.  These mossy beds are found in steep, shaded areas of high humidity close to the stream.  However, it has also been collected on snow on the sagebrush desert near Promontory, Utah, where no obvious patches of moss were present.


Biology:  Nothing is known of immature stages or life history.


Notes:  This species is a member of the californicus species group with males having a large hood with medial ridge.  The only difference between this species and B. californicus is the apical femoral spine found in the latter species.  This character is somewhat unstable and these two nominal species may, in fact, be regional populations of a single species.


The name coloradensis comes from the state in which the first specimens were collected.




Byers, G.W. 1955. A new species of Boreus (Mecoptera: Boreidae) from Colorado. Occasional Papers of the Museum of Zoology, University of Michigan, 562:1-4.


Byers, G.W. and S.R. Shaw.  1999 [2000].  A new species of Boreus (Mecoptera: Boreidae) from Wyoming.  Journal of the Kansas Entomological Society  72(3):322-326.




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