Boisea rubrolineatawestern boxelder bug

Geographic Range

Western boxelder bugs (Boisea rubrolineata) are found in the Nearctic region. Their range extends along the west coast, as far north as central British Columbia and as far south as southern California. The eastern border of their range includes much of Idaho, Utah, and New Mexico, as well as southwestern Colorado. Western boxelder bugshave not been reported outside of their native range. (Carroll, 2014)


Western boxelder bugs prefer to live in areas where there are trees and other vegetation as food sources. This includes natural areas, but also urban, suburban, and agricultural areas. They are mostly limited to temperate climates, but can inhabit less vernal biomes such as deserts and mountains. Western boxelder bugs are uncommon in mountainous areas, but have been reported in places like Del Norte and Humboldt, California. These insects tend to stay at lower to moderate elevations, with the lowest recorded at 6 m above sea level in Napa, California. (Carroll, 2014)

  • Range elevation
    6 to 1955 m
    19.69 to 6414.04 ft

Physical Description

Western boxelder bugs are closely related to boxelder bugs (Boisea trivittata), and are similar in appearance. Both species have small, black, ovoid bodies with red-orange lines around the edges of their forewings and thoracic sclerites. The main physical difference between the two species is that western boxelder bugs have additional red-orange markings that follow the internal venation of their forewings in addition to the forewing borders.

Western boxelder bugs have small, spade-shaped heads with large, red, lateral compound eyes. They also have two ocelli, or simple eyes, which detect changes in light and likely aid in the perception of their environment. Western boxelder bugs have a conspicuous notch on the anterior portion of their first thoracic segment. This feature is common in other insects of the subfamily Rhopalinae. Western boxelder bugs have black legs with orange coxae and long mouthparts adapted for piercing plant tissue and sucking out nutrients. It is thought that the bright orange and black coloration of western boxelder bugs is aposematic, warning predators of their toxicity. Western boxelder bugs are approximately 13 mm long. Male and female western boxelder bugs are very similar, although the females are slightly larger. (Elliott, et al., 2018; NPIC, 2021; Schwarz, 2008)

  • Sexual Dimorphism
  • sexes alike
  • female larger
  • Range length
    10 to 14 mm
    0.39 to 0.55 in


Western boxelder bugs develop from eggs, laying dormant through the winter after they are laid, emerging in the spring as first instar nymphs. Alternatively, they may emerge later in summer as a second yearly generation. After hatching, first instar nymphs go through incomplete metamorphosis consisting of five instars before becoming adults, which look very physically similar to the nymphal stages. Nymphs slowly increase in size and physiological development as they progress through each instar stage, until they reach maturity. Nymphs that emerge from eggs in the late summer or fall reach adulthood before winter, during which they enter diapause, suspending development and reproduction until spring when the weather is warmer. (Schwarz, 2008)


There is very little information available on specific mating systems of western boxelder bugs. However, they are closely related to boxelder bugs (Boisea trivittata), which are promiscuous. It is likely that western boxelder bugs have a similar mating system. (Terry, 2021)

Western boxelder bugs typically have two mating seasons, depending on the timing of emergence. For individuals that emerge as nymphs early in the year, mating occurs in the middle of summer. For individuals that matured in the prior year and entered diapause in winter, mating occurs in spring after emergence from diapause. Females typically lay about 10 eggs in a clutch, which then hatch as first instar nymphs after approximately two weeks. First instar nymphs take about 60 days to reach sexual maturity as adults. (Schwarz, 2008)

  • Breeding interval
    Frequently during the breeding season
  • Breeding season
    Spring, Mid-summer
  • Average eggs per season
  • Average age at sexual or reproductive maturity (female)
    60 days
  • Average age at sexual or reproductive maturity (male)
    60 days

There is no research regarding parental investment in western boxelder bugs.


There is little data on the lifespan of western boxelder bugs. However, individuals that emerge in the spring typically live until the end of the breeding season in the fall, and individuals that emerge later in summer typically overwinter and die after reproducing in the spring. Thus, the lifespan of western boxelder bugs is estimated to be between 6 and 12 months. (Schwarz, 2008)

  • Typical lifespan
    Status: wild
    6 to 12 months


Western boxelder bugs are specialized to live and feed on trees. They are capable of flying to tall branches or climbing on surfaces such as bark or leaves. However, they are not entirely restricted to living on trees. Western boxelder bugs crawl on the ground and are a common nuisance species in human-made structures. Western boxelder bugs are diurnal insects and can fly up to two miles to look for suitable feeding sites. While they are often found alone, they aggregate in groups to mate or feed. (NPIC, 2021; Schwarz, 2008)

One notable behavior of western boxelder bugs is sunbathing as a means of sanitation. They tend to aggregate in sunny places, at which point they release a monoterpene that they smear on their exoskeletons. This chemical does not have a use as a pheromone, but keeps the fungal pathogen Beauveria bassiana from reproducing. The fungus dies off naturally, but without creating or spreading spores, so western boxelder bugs that apply this chemical can keep their cuticles clear of fungal infection. (Schwarz, et al., 2012)

Home Range

There is no record of home range size specified for western boxelder bugs.

Communication and Perception

Western boxelder bugs, like many other insects, perceive their environment visually and through touch. Additionally, western boxelder bugs are sensitive to sound and vibrations due to setae, or sensitive hairs, on their bodies.

Western boxelder bugs communicate with each other primarily with visual and chemical cues. They also communicate through touch when aggregating in large numbers. (NC State, 2015)

Most importantly, these insects communicate chemically through pheromones and allelochemicals. Their antennae have receptors to such chemicals that allow them to interact with their surroundings and other organisms. One of their most notable pheromones is 2-Phenylethanol, which is an aggregation and mate-attractant pheromone. During mating seasons in the summer and spring, western boxelder bugs release this pheromone, signaling others in the area to gather on one tree and seek mates. Western boxelder bugs also receive chemical cues from their host plants. Volatiles from these plants cue the bugs to their presence and the readiness of their fruits and seeds for feeding (Schwarz, 2008). (NC State, 2015; Schwarz, 2008)

Food Habits

Western boxelder bugs are primarily frugivores and granivores. They eat fruits and seeds from trees like boxelder (Acer negundo), maple (Acer), ash (Fraxinus), bigleaf maple (Acer grandifolium), goldenrain tree (Koelreuteria paniculata), Western soapberry (Sapindus saponaria), apple (Malus), peach (Prunus persica), kiwi (Actinidia deliciosa), almond (Prunus amygdalus), cherry (Prunus avium), grape (Vitis vinifera), plum (Prunus domestica), and pear (Pyrus spp.). They do not typically do enough damage to be economically impactful, but can damage fruits and seeds of these trees. (NPIC, 2021; UC IPM, 2017)

  • Plant Foods
  • seeds, grains, and nuts
  • fruit


Western boxelder bugs are black and orange. These colors are aposematic, indicating to predators that they may be poisonous. Western boxelder bugs are not truly poisonous, but exude a distasteful odor when injured or killed. (Davidson, 2018)

Predators of western boxelder bugs mostly include rodents and birds. Species in the order Rodentia, such as rats, chipmunks, and mice have been reported to prey on western boxelder bugs, as have birds like geese and ducks (family Anseridae) as well as guinea hens and chickens (family Galiiformes). Western boxelder bugs are often eaten by other arthropods, such as spiders (order Araneae), wheel bugs (Arilus spp.), and praying mantises (order Mantodea). (Davidson, 2018)

Ecosystem Roles

Western boxelder bugs typically live and feed on trees in the Acer genus. Their main host species is boxelder maple (Acer negundo), but they also use silver maple (Acer saccharinum) and red maple (Acer rubrum). Additionally, western boxelder bugs may feed on ash trees (genus Fraxinus) , as well as orchard fruits like pear, plum, and cherry. Western boxelder bugs will primarily live on and feed from pistillate (female) trees, as these are the ones bearing seeds and fruit. (NPIC, 2021; Schwarz, et al., 2012)

Western boxelder bugs are also well known hosts of the parasitic trypanosome Leptomonas podlipaevi, and the fungal pathogen Beauveria bassiana. (Schwarz, 2008; Yurchenko, et al., 2006)

Species Used as Host
  • Boxelder trees (Acer negundo)
  • Red maple trees (Acer rubrum)
  • Ash trees (Fraxinus)
  • Silver maple (Acer saccharinum)
  • Pear (Pyrus)
  • Kiwi (Actinidia deliciosa)
  • Almond (Prunus amygdalus)
  • Apple (Malus)
  • Cherry (Prunus avium)
  • Peach (Prunus persica)
  • Plum (Prunus domestica)
  • Grape (Vitis vinifera)
Mutualist Species
  • plum trees, and on grapes
Commensal/Parasitic Species
  • Leptomonas podlipaevi
  • Beauveria bassiana

Economic Importance for Humans: Positive

There is no known notable economic importance of western boxelder bugs for humans except for as food for species that hunt pest insects, like birds, or as a research subject for hemipteran behavior.

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

These insects are typically categorized as nuisance pests due to their presence in homes and businesses. They frequently enter buildings, and can cause mess with their feces. Also, when western boxelder bugs are killed or threatened, they produce a smelly odor. Fortunately, though these insects gather inside, they do not mate there and therefore cannot grow in numbers in human furnishings.

Western boxelder bugs can also cause marginal damage to ornamental trees, though the level of damage is rarely significant. Their feeding mainly causes puckering and disfigurement on fruit. (UC IPM, 2017)

  • Negative Impacts
  • crop pest
  • household pest

Conservation Status

There is no special conservation status for western boxelder bugs as they are common throughout their range.


Amy Bagby (author), Colorado State University, Amy Bagby (editor), Colorado State University, Genevieve Barnett (editor), Colorado State University, Galen Burrell (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


uses sound to communicate


living in landscapes dominated by human agriculture.


having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.


Referring to an animal that lives in trees; tree-climbing.

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.


uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.


a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.

  1. active during the day, 2. lasting for one day.

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.


an animal that mainly eats fruit


an animal that mainly eats seeds


An animal that eats mainly plants or parts of plants.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body


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.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

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


generally wanders from place to place, usually within a well-defined range.


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


an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).


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


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season


remains in the same area


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


associates with others of its species; forms social groups.


lives alone


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.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


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


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


Carroll, S. 2014. "Boisea rubrolineata" (On-line). Soapberry Bugs of the World. Accessed November 29, 2021 at

Davidson, E. 2018. "What Eats Boxelder Bugs" (On-line). Sciencing. Accessed December 30, 2021 at

Elliott, L., H. Nendick-Mason, B. Moisset, R. McLeod, D. Ferguson, B. Velov. 2018. "Species Boisea rubrolineata - Western Boxelder Bug" (On-line). BugGuide. Accessed December 03, 2021 at

NC State, 2015. "Insect Communication" (On-line). Agriculture and Life Sciences. Accessed December 29, 2021 at

NPIC, 2021. "Boxelder Bugs" (On-line). National Pesticide Information Center. Accessed December 03, 2021 at

Schwarz, J. 2008. The chemical ecology of host foraging, aggregation, and prophylactic microbial defense in the western boxelder bug, Boisea rubrolineata (Barber) (Heteroptera: Rhopalidae). Department of Biological Sciences Master's Defense at Simon Fraser University, 0:0: 1-188. Accessed December 03, 2021 at

Schwarz, J., Z. Punja, M. Goettel, G. Gries. 2012. Do western boxelder bugs sunbathe for sanitation? Inferences from in vitro experiments. Entomologia Experimentalis et Applicata, 145: 38-49. Accessed December 30, 2021 at

Terry, A. 2021. "Boisea trivittata boxelder bug" (On-line). Animal Diversity Web. Accessed December 23, 2021 at

UC IPM, 2017. "Pests in Gardens and Landscapes: Boxelder Bug" (On-line). University of California Agriculture and Natural Resources: Statewide Integrated Pest Management Program. Accessed December 23, 2021 at

Yurchenko, V., J. Lukeš, X. Xu, D. Maslov. 2006. An Integrated Morphological and Molecular Approach to a New Species Description in the Trypanosomatidae: the Case of Leptomonas podlipaevi n. sp., a Parasite of Boisea rubrolineata (Hemiptera: Rhopalidae). Journal of Eukaryotic Microbology, 53(2): 103-111.