Mymaridae | |00.3 | | | | | Empididae | |01.3 | | | | | Cecidomyiidae | | | | |04.0 | | Trachinidae | |00.7 | | | | | Simulidae | |06.7 |20.0 | | | | Tabanidae | | | | |06.0 | | Chironomidae | | | | |06.0 | | Not identified to family| |01.0 | | | | | Orthoptera | | | | | | | Locustidae | |07.7 | | | | | Tettigoniidae | | |03.0 |70.0 | | |09.0 Tetrigidae | | | | |06.0 | | Homoptera | | | | | | | Fulgoridae | |05.0 | | | | |01.0 Insect egg | |00.7 | | | | | Plants | | | | | | | Cyanophyceae | | 09.0| | | | 99.0| 20.0 Cyperaceae | | 02.0| | | | | 01.0 Zannichellia palustris | | 00.3| | | | | Vascular remains | 55.0| | | 27.0| | | | | | | | | | Miscellaneous | | | | | | | Sand | | 00.7| | | | | Pharyngeal tooth | | 00.3| | | | | +-----+-----+-----+-----+-----+-----+----- Total (%) |100.0| 99.8|100.0|100.0|100.0|100.0|100.0 ------------------------------+-----+-----+-----+-----+-----+-----+----- Spawning apparently occurs when river levels recede to the seasonal lows. In late summer, temperatures of these rivers probably are maximal, their turbidities are reduced, and their sandy bottoms are stable. Underhill (1959) reports that this species is rare in the Vermillion River, a northeastern tributary of the Missouri River, except in autumn when large numbers occur near the mouth of the river. We suspect that this is associated with spawning. [Illustration: PLATE 21 Distribution of collections examined.] [Illustration: PLATE 22 _Hybopsis gracilis gracilis._ Missouri River, Thurston County, northeast of Macy, Nebraska. Largest specimen 87.5 mm standard length.] [Illustration: PLATE 23 _Hybopsis gracilis gulonella._ Pecos River, San Miguel County, 3 miles south of town of Pecos, New Mexico. Largest specimen 91 mm standard length.] [Illustration: PLATE 24