570 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 512. 



13. THE NYMPHS OF WESTERN GOMPHUS. 

 The following characterization of the nymphs of GompJius is from 

 Doctor Needham's Aquatic Insects in the Adirondacks (pp. 435- 

 436 and 443) :' 



Middle legs not more approximate than fore legs at base, the fourth segment of the 

 antenna a mere rudiment, much shorter than the third segment is wide; tenth abdomi- 

 nal segment much shorter than ninth. Wing cases laid closely parallel along the back; 

 lateral lobe of labium ending in a sharp, incurved hook. Abdomen only slightly 

 depressed, ovate to lanceolate in outline, at least twice as long as wide. Third joint 

 of antenna elongate, linear, little flattened. Dorsum of ninth abdominal segment 

 rounded, or with a low, obtuse median longitudinal ridge. 



GOMPHUS INTRICATUS, nymph. 



A thin skinned, whitish exuvia with sooty tints on the abdomen; 

 moderately slender. Sm-face very sparsely coated with exceedingly 

 minute bristle-like hau's. This is a typical Stylurus nymph and is 

 distinguished by the following characters: 



Mentum of labium transparent, tapering proximad with sinuate 

 sides, width of posterior margin one and three-fourths times in that 

 of anterior margm. Middle lobe convex, with a fringe of about 60 

 bristlelike scales. Each lateral lobe broad at base, with a crescentic 

 tip that is suddenly contracted to a large terminal point standing at 

 right angles to the lobe; three large and two smaller rounded teeth on 

 the concave edge posterior to the termmal point. Burrowing hooks 

 rudimentary on both first and second tibiae. Wing pads reaching 

 to segment 4. Abdomen lanceolate, very slightly contracted at base 

 of segment 9, subcircular in cross section. A dorsal groove on seg- 

 ments 3-7. No middorsal hooks or spmes. Segments 6-9 with 

 lateral hooks, those on 9 one-half the length of segment 10. Seg- 

 ments 2-9 subequal in length; segment 10 one- third the length of 

 segment 9, and twice as wide as long. Appendages twice length of 

 10. (See figs. 315 and 321-323.) 



Length, 27 mm.; abdomen (including appendages), 19; hind femur, 

 4. Width of head, 5 mm. ; abdomen, 6. 



Described from 4 female nymphs collected on the Humboldt River 

 at Lovelocks, Nevada, August 10, 1914. These were taken from 

 dead weed stems 2 feet above the lowest level of the river. At this 

 point was a deep hole (3 feet) with a muddy bottom, the greatest 

 part t)f the river bed bemg composed of a coarse grit. 



GOMPHUS OLIVACEUS NEVADENSIS.^ nymph. 



A large, slender, whitish exuvia, sparsely covered with minute 

 bristlehke hairs. This is a typical Stylurus nymph and is distin- 

 guished by the following characters: 



» BuU. 47, N. Y. State Mus., 1901. 



2 A form of olivaceus nymph has been described by Needham from Seattle, Washington, as sobrinut 

 in Proc. U. S. Nat. Mus., vol. 27, 1904, p. 692. 



During August, 1915, 1 found the same form of olivaceus on the Owens River, Inyo County, California, 

 as that found at Sacramento, which is the typical olivaceus. The nymphs of the Owens River olivaceus 

 were identical with those of Oomplius olivaceus nevademis. 



