Part of the Assassin Bug family, masked hunter adults are approximately 10-12mm in length.  They are very dark brown to black in color and have a narrow head with a distinct beak protruding from below.  Their front legs are slightly thickened in comparison to their other legs, which is an adaptation for grasping and holding their prey.  Nymphs are typically a gray-brown color; however, their sticky bodies are typically covered in debris such as lint, sawdust and other debris to provide camouflage.  In areas where materials are readily available, nymphs may become heavily covered and resemble a walking ball of dust and lint.  This measure is necessary in order for the nymphs to ambush their prey.  Masked hunters are predators of other insects and impale and paralyze their prey with mouthparts capable of both piercing and sucking.  Although masked hunters have been known to bite humans, it typically only occurs in defense or when provoked.  The bites are painful and may result in localized swelling which may last upwards of a few days.  Masked hunters are believed to occur statewide in Colorado with their range increasing in part by transportation by humans.  They are originally a European species.

Masked hunters have a two year life cycle.  Adults are commonly seen from late June through early August.  Due to their attraction to lights, the winged adults are frequently seen near lighting during high activity times of year.  Masked hunters may complete their development both indoors and outdoors.  For this reason and their hunting habits they are sometimes referred to as “bed bug hunters”, although they typically feed on a variety of different insects.  Eggs are laid in crevices as small masses and the resulting first stage nymphs will begin to hunt small flies, springtails and other small prey that they are capable of subduing.  After continued development, it is believed that it is the third instar nymph stage that overwinters during the first year.  Further development occurs during the masked hunter’s second year of life resulting in a fifth instar nymph, which is the final immature stage of development.  Overwintering occurs again at this stage with a molt to adulthood occurring the following spring.  Masked hunters are considered to be beneficial insects due to their hunting and feeding habits.  Household control is not typically necessary.