Figure 7.12.1 Platydracus violaceus (Gravenhorst), dorsal habitus. 7.12.2 P. violaceus, lateral view of left elytron. 11.19.1 P. violaceus, from under the bark of a fallen maple.

This species is easily recognized by the combination of a purple-blue metallic dorsal body and characteristic pattern of pale abdominal setae (Fig. 7.12.1). It may be confused with P. viridanus (Horn), which normally has a bronze metallic reflection but can appear purple in specimens from traps with killing agents. Platydracus viridanus also has a more transverse pronotum that is distinctly wider than the head, while in P. violaceus,the pronotum is subequal in width to the head. Platydracus violaceus also has a dark elytral epipleuron (Fig. 7.12.2) and completely dark legs, while in P. viridanus the ventral margin of the epipleuron is paler than the rest of the elytron and the legs are usually at least partially pale.

This species is distributed broadly in eastern North America. Its range in ECAS is given by Map 24. It is newly recorded from the state of Vermont based on a historical record; it very likely still occurs there:

UNITED STATES: VT: Addison Co., Salisbury, 43.9 -73.1, 5-VII-1895, 1 (MCZ)

Eastern Canada: ON, QC, NB, NS, PEI
Adjacent U.S.: MI, IN, OH, PA, NY, VT, NH, ME (All ECAS states)

Platydracus violaceus has been collected in ECAS from April to December, with an increase in abundance occurring in May.

Platydracus violaceus is a common species found in mesic to swampy forests, primarily under the loose bark of dead hardwood trees including oaks, maples, basswood, horse chestnut, hackberry, beech, and hickory. It occurs less frequently under the bark of white pine, in rotting wood, and under logs. The few records in rotting fungi, on carrion, or on dung probably do not reflect habitat preferences. Larvae were found to readily consume various insect larvae occurring under bark (Newton 1973) and it is likely that adults have similar dietary habits.  Mature larvae are collected in the early spring (Hoebeke 1978; A. Brunke personal observations) indicating that this species overwinters in this stage.  Larvae form pupal cells out of frass and wood debris and are sometimes parasitized by the proctotrupid Codrus carolinensis (Ashmead) (Hoebeke 1978).  Adults appear to emerge later in spring (April-May).  Jennings and Tallamy (2006) found this species in a relatively undisturbed secondary forest but not in an isolated woodlot of similar tree species composition. Similarly, Majka (2010) found this species in an old growth forest remnant in Prince Edward Island, a province where it was not known previously. It was hypothesized that forestry practices were responsible for this species’ absence in previous collections made elsewhere in the province. Based on our collection data, this species does not require old growth but is usually found in forests with at least some mature trees.  Smetana and Davies (2000) noted that P. violaceus was a preoccupied name and replaced it with a younger synonym, P. cupripennis (Melsheimer, 1844), but P. violaceus was conserved as the valid name for this species by Opinion 2039 of the International Commission on Zoological Nomenclature (ICZN 2003).