Figures: 25, 56, 129, 192, 240
In addition to the Rhithrogeninae characteristics, the following combination of characteristics will identify the genus:
Larvae of Spinadis are differentiated from all other Nearctic genera by the combination of having only two well-developed caudal filaments, interfacing setae on the caudal filaments, sparse setae on the legs, and well-developed paired submedian tubercles on the head and thorax (Fig. 25). The relatively long, narrow legs of these predatory larvae are atypical of the family in general. The closely related Anepeorus lacks well-developed tubercles on the head and has numerous long, fine setae on the legs.
Males of Spinadis are identified by having foretarsi that are shorter than the foretibiae and an anteriorly truncate head capsule (Fig. 129). Females differ from other North American Rhithrogeninae by the combination of having a transverse suture (as in Fig. 115), a rounded costal process on the hindwings (Fig. 192), and a truncate head capsule (Fig. 129).
Eastern Nearctic (Fig. 240).