Cimex pilosellusbat bug

Geographic Range

Cimex pilosellus is found in North America, most commonly across the northern United States and Canada. Cimex pilosellus may be found both in urban and campestral settings following their bat hosts and occasionally spreading to humans. It has two common names: batbugs and bedbugs. They are often called batbugs because they are found almost exclusively on bats in North America. However, all Cimicidae have very similar morphologies, and on the occasion that Cimex pilosellus infests a human residence, it will often be confused for common bedbugs. (Dooley, et al., 1976; Ford and Stokes, 2006)


Adult Cimex pilosellus are nidiculous parasites of bats. As their morphology is poorly adapted for holding on to their common hosts while they are in flight, they live primarily in bat roosts. For this reason the females of the bat host species are generally more infested, as they must spend more time in the roosts to rear young. Larval nymphs are deposited in the roosts to locate and feed for themselves.

Bats are generally more active at higher temperatures, leading to frequently empty roosts and a lack of food for Cimex pilosellus. During periods of increased temperature, Cimex pilosellus are more likely to leave the bat roosts and attempt to infest a human habitat, as a result of the increased absence of their regular bat hosts. They may then attempt to infest any number of mammal roosts, the most familiar being a human home. When Cimex pilosellus finds its way into a human home, it behaves as other Cimicidae do: living in dark cracks and crevices, usually waiting until nightfall to come and feed on sleeping people. ("Just the Facts...Bed Bugs", 2005; Chilton, et al., 2000; Valdez, et al., 2009; Webster and Whitaker, 2005; Wilson and Galloway, 2002)

Physical Description

Cimex pilosellus begin as eggs and undergo hemimetabolous indeterminate transformation through approximately 5 nymphal stages prior to the molt to adulthood. Nymphs resemble adults in morphology, excluding the presence of genitalia.

Adult Cimex pilosellus are oval in shape, 4 to 5 mm in length, and like most Cimex species, are red or mahogany in color. They are wingless and have 6 legs, and after a blood meal they become swollen and darker in color. Distinguishing features of Cimex pilosellus from other species in the Cimex genus include longer hair, the second and third antennal segments are equal in length, and the inner margin of the hemelytra is straight and longer than the scutellum. There is slight sexual dimorphism in Cimex pilosellus as females are generally larger than males. ("Just the Facts...Bed Bugs", 2005; Cornstock, 1949)

  • Sexual Dimorphism
  • female larger
  • Range length
    4 to 5 mm
    0.16 to 0.20 in
  • Average length
    5 mm
    0.20 in


Cimex pilosellus begins life as an egg, and once it hatches the nymph looks very similar to the adult except that nymphs are smaller, translucent, and lacking genitalia. Members of the bedbug family Cimicidae exhibit hemimetabolous indeterminate development, molting up to five times before reaching the adult stage, with each molt requiring a blood meal. Females are larger than males, and require a larger blood meal by the fifth instar. Each instar stage lasts from 3 to 5 days. The entire life cycle generally is contained on the bat roost on which a nymph hatches. Occasionally an individual in any stage of development may be carried off while still feeding on the bat to another roost, allowing for dispersal of the parasite. ("Just the Facts...Bed Bugs", 2005; How and Lee, 2010; Reinhardt and Siva-Jothy, 2007)


Little is known about the mating systems of Cimex pilosellus. The species is considered polygynandrous and there is no evidence suggesting that there is any sexual selection or courtship rituals. (Reinhardt, et al., 2003; Richardson, et al., 2003)

The mating behavior of Cimex pilosellus has been very sparsely studied. The closely related common bedbugs have been studied in great detail and, with such similar morphology to C. pilosellus, their mating behavior may be similar. Cimicidae males have been known to mount anything which moves and is approximately the expected size of another Cimicidae. If the mounted organism is a female Cimicidae, the male will begin attempting to traumatically inseminate her. It is unclear as to how the males distinguish, but chemical and behavioral signals are believed to be involved.

Cimex pilosellus, like all members of the bedbug family Cimicidae, practice a very unorthodox method of reproduction termed traumatic insemination, where the male pierces the abdominal integument and injects the sperm directly into the wound. To counteract the harmful mating ritual, females have a unique organ called the spermalege. The spermalege serves to direct and store the sperm away from the hemocoel (the space between organs), as sperm in the hemocoel is generally fatal. The spermalege is believed to also aid in defense against pathogens resulting from the reproductive wound.

Feeding is a required prerequisite for mating, as males greatly prefer to mate with a female who has either just fed or is in the process. Regular feeding is necessary for egg production, and a female may undergo as many as five traumatic inseminations from different males per feeding. Males do not use the genital tract for insemination. Mating for females results in a 30% decrease in lifespan.

Females can store sperm for up to 50 days after insemination, and as long as they have regular blood meals to replenish nutrients necessary for egg development, females continue laying eggs using their sperm reserves. Females may lay up to 5 eggs per day. On average females require 2 to 3 days to develop and deposit eggs, and 5 to 7 days for the eggs to hatch. After hatching, each nymph requires 3 to 5 days to molt and develop into the next stage until they reach adulthood. The entire metamorphosis may take 30 to 200 days. Cimex pilosellus are reproductively mature immediately after molting into the adult phase. ("Just the Facts...Bed Bugs", 2005; How and Lee, 2010; Reinhardt and Siva-Jothy, 2007)

  • Breeding interval
    Female batbugs can lay 5 eggs per day for up to 50 days following mating.
  • Breeding season
    Batbugs breed year-round.
  • Average eggs per season
    5 per day
  • Range gestation period
    5 to 7 days
  • Range age at sexual or reproductive maturity (female)
    30 to 200 days
  • Range age at sexual or reproductive maturity (male)
    30 to 200 days

Like all studied Cimicidae, Cimex pilosellus exhibits no parental involvement with the young after laying of the eggs. The males typically will leave the female after mating in search of another blood meal or another female, and the final interaction the female has with her progeny is control over when to lay the eggs. (Reinhardt and Siva-Jothy, 2007)

  • Parental Investment
  • no parental involvement


Lifespans of Cimex pilosellus have not been studied in detail, but longevity of closely related Cimex hemipterus has been studied, which may give insight to the lifespan of Cimex pilosellus. Wild adults have been found to live for approximately 7 months. Lifespan of Cimicidae in captivity has been found to depend more on whether or not the females mate in their lifetime, with an average decrease in longevity of 30% for mated females. (How and Lee, 2010; Reinhardt and Siva-Jothy, 2007)

  • Average lifespan
    Status: wild
    7 months
  • Average lifespan
    Status: captivity
    7 months


Cimex pilosellus is the most common Cimicidae nidiculous parasite of bats across North America. They usually live in the roosts of bats, waiting for their hosts to return home to feed. Cimex pilosellus prefers to feed when the host is resting or has minimal activity. Feeding generally takes 3 to 15 minutes and when not feeding the parasite stays hidden or looks for mates. Eggs are laid inside the nest and the nymphs must find hosts themselves for sustenance.

Cimex pilosellus has the potential to become a parasite of humans, filling the niche of other, more common species of Cimicidae. If their bat hosts do not return to the roosts for too long and the parasite has the opportunity to move into a human dwelling, it may choose to relocate into nearby households. In this instance C. pilosellus adopts common bedbug behavior, living in the folds of mattresses and blankets, or in dark cracks in the walls venturing out at night to feed on sleeping people to continue its life cycle. (How and Lee, 2010; Reinhardt and Siva-Jothy, 2007; Reinhardt, et al., 2003)

Home Range

The exact home range of Cimex pilosellus is unknown, however most individuals spend their entire lives within the same bat roost in which they hatched as nymphs.

Communication and Perception

Cimex pilosellus, along with all other Cimicidae, have a thorax covered in sensory hairs. They also have compound eyes and long antennae on their head to perceive their environments.

While the mechanisms of communication have not been well studied for Cimex pilosellus specifically, it is believed that along with being morphologically similar, all members of the Cimidae family use similar methods of communication. Specifically, mechanisms of reaction to heat, carbon dioxide, and assorted other pheromones have been tested in Cimex lectularius. Tested Cimex lectularius individuals display an attraction to increased temperature, preference to higher concentrations of carbon dioxide, and various responses to chemicals secreted by other Cimicidae. (Ford and Stokes, 2006; Siljander, 2006)

Food Habits

Cimex pilosellus is a nidiculous parasite which feeds on the blood of mammals, most commonly bats, during all stages of its development except while inside the egg. They generally prey on their hosts during times of host inactivity, and need to eat approximately once every ten days. Each instar needs at least one blood meal before molting and developing into the next stage. (Chilton, et al., 2000; Reinhardt and Siva-Jothy, 2007; Siljander, 2006)

  • Animal Foods
  • blood


Known predators of Cimex pilosellus include spiders, pseudoscorpions and ants.

The use of alarm pheromones by Cimicidae have been well documented, which are used to warn other Cimicidae of dangers such as predators, ant attacks, or injury. These pheromones illicit an avoidance response directly proportional to the concentration produced. (Reinhardt and Siva-Jothy, 2007)

  • Known Predators

Ecosystem Roles

Cimex pilosellus has no definite ecosystem role aside from parasitizing its common bat hosts. There is no documentation of Cimex pilosellus serving as a vector for any disease or even causing mortality in its bat hosts. The only known effect of Cimex pilosellus on a host is that when population numbers are too high, entire bat colonies may abandon an infested roost in search of another. Cimex pilosellus preferentially parasitizes bats, and on the rare occasion they have been found on other hosts, humans included, there was no indication that they were anything other than a nuisance.

Cimex pilosellus is host to several known parasites including fungi, bacteria, and mites. (Chilton, et al., 2000; Main, 1979; Pearce and O'Shea, 2007; Valdez, et al., 2009; Webster and Whitaker, 2005; Wilson and Galloway, 2002)

Species Used as Host
Commensal/Parasitic Species
  • fungi (Aspergillus flavus)
  • bacteria (Serratia)
  • mites (Parasitiformes)

Economic Importance for Humans: Positive

Cimex pilosellus has no economic benefit to humans. ("Just the Facts...Bed Bugs", 2005)

Economic Importance for Humans: Negative

Cimex pilosellus is an uncommon household pest. In a rare case of household infestation, there is an economic cost to eradicate the population. (Cornstock, 1949)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Cimex pilosellus has not been thoroughly studied and currently has no conservation status. As prolific breeders, their populations are likely large and they are easily spread to new habitats by using their highly mobile hosts.


Aleksey Mishulin (author), University of Michigan-Ann Arbor, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Rachelle Sterling (editor), Special Projects.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


chemicals released into air or water that are detected by and responded to by other animals of the same species


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


an animal that mainly eats blood


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.


living in residential areas on the outskirts of large cities or towns.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


living in cities and large towns, landscapes dominated by human structures and activity.


uses sight to communicate

year-round breeding

breeding takes place throughout the year


U.S. Army Center for Health Promotion and Preventive Medicine. Just the Facts...Bed Bugs. 18-018-0105. Aberdeen Proving Ground, Maryland: Entomological Sciences Program. 2005. Accessed February 09, 2010 at

U.S. Department of Agriculture Forest Service. The Hemiptera: Heteroptera of the Columbia River basin, Western United States. [Report Number Unknown]. Walla Walla, WA: [Publisher Unkown. 1995. Accessed February 09, 2010 at

Chilton, G., M. Vonhof, V. Peterson, N. Wilson,. 2000. Ectoparasitic insects of bats in British Columbia, Canada. Journal of Parasitology, 86/1: 191-192. Accessed February 06, 2010 at

Cornstock, J. 1949. An introduction to entomology. Ithaca, New York: Cornstock. Accessed February 06, 2010 at

Dooley, T., J. Bristol, A. Canaris. 1976. ECTO PARASITES FROM BATS IN EXTREME WEST TEXAS AND SOUTH CENTRAL NEW-MEXICO USA. Journal of Mammalogy, 57/1: 189-191. Accessed February 06, 2010 at

Feingold, B., E. Benjamini, D. Michaeli. 1968. The Allergic Responses to Insect Bites. Annual Review of Entomology, 13: 137-158. Accessed February 06, 2010 at

Ford, B., D. Stokes. 2006. Bug's Eye View. infocus, 3: 5-15. Accessed February 09, 2010 at

How, Y., C. Lee. 2010. Fecundity, nymphal development and longevity of field-collected tropical bedbugs, Cimex hemipterus. Medical and Veterinary Entomology, 24/1. Accessed March 07, 2010 at

Main, A. 1979. Virologic and serologic survey for eastern equine encephalomyelitis and certain other viruses in colonial bats of New England. Journal of Wildlife Diseases, 15/3: 456. Accessed February 09, 2010 at

Norihiro, U. 2004. Chromosome behavior of the cimex pilosellus complex (Cimicidae: Hemiptera). Chromosoma, 14/5: 511-521. Accessed February 06, 2010 at

Pearce, R., T. O'Shea. 2007. Ectoparasites in an urban population of big brown bats (Eptesicus fuscus) in Colorado. Journal of Parasitology, 93/3: 518-530. Accessed February 06, 2010 at

Pearce, R., T. O'Shea, V. Shankar, C. Rupprecht. 2007. Lack of association between ectoparasite intensities and rabies virus neutralizing antibody seroprevalence in wild big brown bats (Eptesicus fuscus), Fort Collins, Colorado. Vector-Borne and Zoonotic Diseases, 7/4: 489-495. Accessed February 06, 2010 at

Reinhardt, K., R. Naylor, M. Siva-Jothy. 2003. Reducing a cost of traumatic insemination: female bedbugs evolve a unique organ. Proceedings of the Royal Society: Biological Sciences, 270: 2371–2375. Accessed March 07, 2010 at

Reinhardt, K., M. Siva-Jothy. 2007. Biology of the Bed Bugs (Cimicidae). Annual Review of Entomology, 52: 351–374. Accessed March 07, 2010 at

Richardson, D., P. Krause, L. Durden. 2003. Northern American Parasitic Zoonoses. Norwell, Massachusetts: Kluwer Academic Publishers. Accessed February 09, 2010 at

Siljander, E. 2006. Foraging and Communication Ecology of bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae). American Entomologist, 52/2: 116-117. Accessed March 07, 2010 at

Valdez, E., R. Christopher, W. John. 2009. Ectoparasites of the Occult Bat, Myotis occultus (Chiroptera: Vespertilionidae). Western North American Naturalist, 69/3: 364-370. Accessed February 06, 2010 at

Webster, J., J. Whitaker. 2005. Study of Guano Communities of Big Brown Bat Colonies in Indiana and Neighboring Illinois Counties. Northeastern Naturalist, 12/2: 221-232. Accessed February 06, 2010 at

Wilson, N., T. Galloway. 2002. The occurrence of the bat bug, Cimex pilosellus (Horvath) (Hemiptera: Cimicidae), in Manitoba, Canada. Proceedings of the Entomological Society of Manitoba, 58/1: 5-7. Accessed February 06, 2010 at