Microtomus

Microtomus species are distinguished from other Reduviidae by their large size, robust body form, and often bold color patterns combining black with contrasting white, red, or creamy markings. Microtomus purcis specifically shows black body with creamy-white bases on the wings and bright red abdominal segments and hind legs. The genus can be separated from the superficially similar wheel bug (Arilus cristatus) by the absence of a dorsal wheel-like crest on the pronotum.

Species occur in dry-mesic woodlands and forests, particularly in areas with standing dead trees. Microtomus purcis has been documented specifically under loose bark of dead chinquapin oak (Quercus muehlenbergii) and shortleaf pine (Pinus echinata). The genus occupies microhabitats that provide shelter during diurnal inactivity.

The genus has a New World distribution spanning North, Central, and South America. Microtomus purcis occurs in the Ozark Highlands of Missouri and Arkansas, with records south of the Missouri River. Microtomus tibialis has been documented in Pernambuco state, Brazil, in Seasonal Dry Tropical Forest (Caatinga) biome. Other species are distributed across Central and South America.

Adult Microtomus purcis has been recorded from September through March in Missouri, with nymphs found during November and December. BugGuide records indicate activity during summer months as well. Observations suggest year-round presence with peak detectability during cooler months when individuals shelter under bark.

Predatory on other arthropods. Microtomus tibialis has been documented preying on the scorpion Physoctonus debilis, representing intraguild predation. Microtomus purcis is presumed to be a generalist predator given its size and the typical feeding habits of large reduviids.

Primarily nocturnal, hiding under loose bark during daylight. Microtomus purcis is attracted to lights at night. When disturbed from shelter, individuals drop and rapidly seek cover in leaf litter. The species has been observed in defensive postures and delivers a powerfully painful bite when handled. One observation describes an adult M. tibialis holding prey with head and body facing downwards while grasping with mouthparts under vegetation.

Arthropod predator functioning as an intraguild predator that coexists with and preys upon other predatory arthropods in shared microhabitats. The documented predation on scorpions indicates complex trophic interactions within predator communities.

Microtomus purcis is sometimes called the "bark assassin bug." The bite is reported as searingly painful, with one account describing penetration of a fingernail by the proboscis resulting in a blood stain under the nail. The species is sought by insect collectors due to its striking appearance.

• Arilus cristatusBoth are large, colorful North American reduviids with bold markings. Arilus cristatus possesses a distinctive dorsal wheel-like crest on the pronotum, which Microtomus lacks.
• ApiomerusBoth are large, colorful New World reduviid genera. Apiomerus species are typically associated with flowers and have different leg modifications for prey capture, while Microtomus is associated with bark and lacks the specialized leg structures.

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Alydidae | Beetles In The Bush
• Reduviidae | Beetles In The Bush | Page 2
• Report of intraguild predation of the scorpion Physoctonus debilis (C. L. Koch, 1840) (Scorpiones: Buthidae) by the assassin bug Microtomus tibialis Stichel, 1926 (Hemiptera: Reduviidae)