ISSN 1911-2173


Platydracus tomentosus (Gravenhorst 1802)

Figure 7.13.1 Platydracus tomentosus (Gravenhorst), dorsal habitus. 7.13.2 P. tomentosus, head and right antenna.


This species is distinguished from other Platydracus by the combination of a completely black body and setae, eyes subequal to the temple (Fig. 7.13.2) and paired patches of black velvet setae on the abdominal tergites (Fig. 7.13.1). The immaculate form of P. fossator could be confused with P. tomentosus, but the former lacks patches of black velvet setae on the abdominal tergites and has eyes that are distinctly longer than the temple. The darkest individuals of P. mysticus are also similar, but have eyes that are distinctly shorter than the temple.


This species occurs in eastern North America, from Ontario to Florida, and west to Nebraska; it also occurs in Cuba. Its range in ECAS is given by Map 23. Platydracus tomentosus is newly recorded from New York and Ohio.

UNITED STATES: NY: 37 specimens. OH: Logan Co., 40.39 -83.85, 8-VIII-1932, 1 (UMSP). Mercer Co., Celina Spring, 40.55 -84.57, IV-1951, E. Klee, 2 (CAS).

Eastern Canada: ON

Adjacent U.S.: MI, IN, OH, NY

Platydracus tomentosus has been collected in ECAS from January to November, with a peak in abundance in May.



Platydracus tomentosus (Gravenhorst) primarily inhabits the edges of lakes and ponds, and slow-moving waterways, where it can be found under stones, wood, and flood debris. It sometimes occurs in forests or in prairies but these individuals may only be dispersing through to the nearest water body. Schmidt (1994) found many adults within 3 meters of a large creek in a pasture, where they were found singly or in pairs in small ‘discus-shaped’ excavations under objects. This species is probably a generalist predator of riparian arthropods, and Schmidt (1994) fed them lampyrid larvae, isopods, adult flies, and elaterid larvae collected from the same location. Larvae burrow readily in soil (Schmidt 1994), unlike the adults, and could be primarily fossorial. There are very few recent records of this species from the northeastern portion of its range (Map 20) and further collecting in favored habitat is necessary to determine whether P. tomentosus is in decline.