Outbreak-species
Guides
Acantholyda
web-spinning sawflies, pine sawflies
Acantholyda is a genus of web-spinning sawflies in the family Pamphiliidae, distributed across Europe, Asia, and North America. Species are associated with coniferous hosts, particularly Pinus and Cedrus. Several species are significant forest pests capable of causing extensive defoliation during outbreaks. Larvae construct silken webs and may enter extended diapause in soil.
Acleris variana
Eastern Black-headed Budworm, Black-headed Budworm
Acleris variana is a tortricid moth endemic to North American coniferous forests, ranging from Cape Breton Island to Alaska. The species is a recurrent epidemic defoliator of coniferous trees, with periodic population outbreaks causing significant forest damage. Larvae feed on multiple conifer genera with regionally variable host preferences. Population trends are strongly influenced by weather conditions, particularly cold, wet periods that increase larval mortality.
Ageneotettix deorum
white-whiskered grasshopper, white whiskers grasshopper, sand grasshopper
Ageneotettix deorum is a medium-sized slant-faced grasshopper widely distributed across North American grasslands. It is frequently the dominant species in mixedgrass and bunchgrass prairie outbreaks, reaching densities of 25 adults per square yard. The species exhibits early-season hatching with nymphal development spanning 40–48 days. Adults are ground-dwelling, diurnal herbivores that feed on grasses and ground litter. Population dynamics show sensitivity to weather and predation, with outbreaks typically building over 3–5 years followed by sudden crashes.
Anabrus simplex
Mormon Cricket
Anabrus simplex, commonly known as the Mormon cricket, is a large flightless shieldbacked katydid (family Tettigoniidae, subfamily Decticinae) native to western North America. Despite its common name, it is not a true cricket. The species is notable for its periodic outbreak populations that form large migratory bands, causing significant damage to rangeland forage and cultivated crops. It exhibits a sex-role reversed mating system where males provide nuptial gifts and females compete for mates. The species has been documented from low-elevation sagebrush steppe to alpine tundra above 11,000 feet.
Boopedon
boopies, ebony grasshopper (B. nubilum), yellow-belly boopie (B. flaviventris), prairie boopie (B. gracile), short-winged boopie (B. auriventris)
Boopedon is a genus of grasshoppers in the family Acrididae, commonly known as boopies. The genus contains at least eight described species distributed across western North American grasslands. Species in this genus are notable for pronounced sexual dimorphism, with males typically winged and darkly colored while females are often larger, flightless, and paler. Several species, particularly B. nubilum (the ebony grasshopper), are significant rangeland pests capable of reaching outbreak densities.
Boopedon nubilum
ebony grasshopper, black-males grasshopper, plains boopie
Boopedon nubilum is a large slant-faced grasshopper inhabiting western North American grasslands. Males are strikingly black with functional wings, while females are large, pale brown, and typically flightless. The species is a specialized grass feeder with documented food preferences that vary geographically. At high densities, it becomes a significant pest of rangeland forage, particularly in the southern mixedgrass and desert prairies of Arizona, New Mexico, and western Texas.
Cephalcia
spruce web-spinning sawflies
Cephalcia is a genus of web-spinning sawflies in the family Pamphiliidae, established by Panzer in 1803. Species are distributed across Europe, North America, and Asia. Larvae feed primarily on conifer needles, particularly spruce (Picea) and larch (Larix), and construct silk webs for protection while feeding. Several species are significant forest pests capable of causing defoliation during population outbreaks. The genus exhibits complex life cycles with variable voltinism, often involving extended diapause in soil-dwelling prepupal stages.
Choristoneura conflictana
large aspen tortrix
Choristoneura conflictana, the large aspen tortrix, is a tortricid moth native to North America. The species undergoes periodic population outbreaks that can severely defoliate trembling aspen stands in parts of Manitoba and Saskatchewan. Adults are active from May through August, with a wingspan of 25–35 mm. The species was first described by Francis Walker in 1863 and ranges across the continent from Alaska to the Atlantic coast.
Epirrita autumnata
Autumnal Moth
Epirrita autumnata, the autumnal moth, is a geometrid moth native to northern Fennoscandia and the Palearctic region. Its larvae feed primarily on mountain birch (Betula pubescens ssp. tortuosa and ssp. czerepanovii) foliage, with outbreaks capable of defoliating extensive birch forests. The species exhibits cyclic population dynamics with outbreak and non-outbreak phases. Eggs overwinter in diapause, showing exceptional cold hardiness with supercooling points reaching −36.5 °C. Adult females suffer substantial predation pressure from invertebrate predators, particularly harvestmen.
Euproctis chrysorrhoea
Brown-tail Moth
Euproctis chrysorrhoea, the brown-tail moth, is a univoltine forest pest with a highly polyphagous larval stage. Populations exhibit phenological plasticity, with larval diapause timing and winter feeding behavior varying based on host plant foliage persistence. The species demonstrates sequential host plant utilization during mass outbreaks and shows evidence of host-associated genetic divergence. Larvae possess urticating setae that pose human health risks.
Malacosoma disstria
Forest Tent Caterpillar Moth
The forest tent caterpillar moth (Malacosoma disstria) is a native North American lasiocampid moth known for its periodic outbreak populations. Unlike its congener the eastern tent caterpillar, it does not construct true silken tents; instead, larvae form silk mats on which they rest between feeding bouts. The species is highly polyphagous on deciduous trees and exhibits gregarious behavior in early instars, becoming more solitary in later stages. Population cycles are regulated by natural enemies including parasitoid wasps, flies, and pathogens.
Melanoplus devastator
devastating grasshopper
Melanoplus devastator, the devastating grasshopper, is a medium-sized spur-throated grasshopper endemic to the far western United States, primarily California, with limited occurrence in Oregon and Washington. It is a major agricultural pest known for irruptive population outbreaks that can cause extensive damage to rangeland forage, orchards, and crops. The species exhibits a unique life history among rangeland grasshoppers, with females entering reproductive diapause during summer and resuming egg development in fall triggered by decreasing photoperiod. When populations explode, nymphal bands and adult swarms migrate from depleted foothill rangelands into valley agricultural areas, sometimes traveling 30 miles or more.
Melanoplus rugglesi
Nevada Sage Grasshopper
Melanoplus rugglesi is a medium-sized spur-throated grasshopper endemic to the cold desert shrublands of the western United States. The species exhibits pronounced phase polyphenism, with solitary and migratory forms differing in body size, wing length, and coloration. Named in honor of entomologist Arthur G. Ruggles, this grasshopper is notable for its extreme migratory behavior and extended outbreak dynamics, with populations persisting at high densities for multiple years.
Neodiprion edulicolus
Pinyon Sawfly, Pinyon Pine Sawfly
Neodiprion edulicolus, the pinyon pine sawfly, is a conifer-feeding sawfly endemic to the Intermountain Region of western North America. The species periodically undergoes population outbreaks causing extensive defoliation of singleleaf pinyon pine (Pinus monophylla), with over 100,000 acres affected during documented events in 1965-1966 in eastern Nevada. Unlike bark beetles and fungi that typically dominate conifer health concerns, this folivore can render host trees commercially unfit for Christmas tree sales. Outbreaks have historically been short-lived, with populations declining due to climatic factors and parasitoid pressure.
Trirhabda canadensis
goldenrod leaf beetle
Trirhabda canadensis, commonly known as the goldenrod leaf beetle, is a leaf beetle in the family Chrysomelidae. It is found in North America and specializes in feeding on goldenrod species (Solidago). Outbreak populations can cause severe defoliation, removing 20-100% of leaf area from host plants. The species has been studied for its ecological impacts on plant communities and its interactions with other herbivores.
Xanthippus corallipes altivolus
Red shanks
Xanthippus corallipes altivolus is a subspecies of the redshanked grasshopper found from foothills to timberline in Colorado and western North America. Adults are medium to large, tan-colored grasshoppers with distinctive red inner hind femora and orange hind tibiae. This subspecies is distinguished from other X. corallipes subspecies by its high-elevation habitat. Populations can cause significant damage to rangeland grasses during outbreak years.
Xanthippus corallipes corallipes
Redshanked Grasshopper, Red Shanks
A large rangeland grasshopper of western North America, adults are present in spring and are conspicuous due to loud crepitation during evasive flight. The subspecies exhibits strong flight capability and feeds almost exclusively on grasses and sedges. Populations normally remain at low densities but occasionally erupt into outbreaks that damage rangeland and crops. Northern populations have a two-year life cycle while southern populations complete development in one year.