Four-spotted grasshopper (Phlibostroma quadrimaculatum)
| Phlibostroma quadrimaculatum Four-spotted grasshopper | |
|---|---|
 | |
| Distribution | |
| Alberta, Saskatchewan, Manitoba, Idaho, Montana, Wyoming, Utah, Colorado, Arizona, New Mexico, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas, Minnesota, Iowa | |
| Taxonomy | |
| Family: | Acrididae |
| Subfamily: | Gomphocerinae |
| Genus: | Phlibostroma |
| Additional resources | |
| Full taxonomy at OSF | |
The four-spotted grasshopper (Phlibostroma quadrimaculatum) is a common medium-sized, ground-dwelling, grassland species found primarily in dry grasslands and prairies of the central and southwestern United States. It is named for the four distinct dark spots typically visible on its hind wings during flight. These grasshoppers are occasionally a rangeland pest during outbreaks along with other species.
Nomenclature
Phlibostroma quadrimaculatum (Thomas, 1871). For full nomenclature, see this taxon's page on Orthoptera Species File
Identification
Despite its name, the four-spotted grasshopper can have three to five spots on the forewings. The spots can be discrete of a crenulate pattern—often compared to jack o’ lantern teeth.[1] It is a striking species that is generally green or brown with black, ivory, and white markings. [2] Adult P. quadrimaculatum lack a slanted face. Their head and pronotum appear to be slightly oversized and broad.[3] When viewed from above the pronotum has two black triangles.[2] Their lateral foveolae aren’t visible. The hind femur is banded and the hind tibiae are orange.[1] The junction of the hind femora and tibiae is black. [2] The pronotum disk contains a medium carina that is broken in the middle. While the lateral carinae is clearly visible, it is constricted in the central region. Wing length ranges, with some wings extending just short of the abdomen to others extending 5 mm past the abdomen. Populations found in the southern range of this species, in areas such as Texas, have more common occurrences of longer wings.[1]
Nymphs of these species can be identified by their relatively large, and moderately slanted-faced head. Their antennae are filiform. Initially, instar 1 nymphs have an ivory colored head, with various bands and stripes around their compound eyes. This ivory turns into green from instar 2 to 5. As these nymphs develop, the dark brown band below their compound eye begins to fade and appear segmented, and a vertical ivory band appears below the compound eye. Their lateral carinae are ivory-colored and become increasingly constricted toward the central region, a trait that is more pronounced in adults of this species. On the anterior central region, there is a pronotal lobe with a diagonal ridge that is ivory. The later instars show a hind tibia that is tan and gray, or sometimes pink.[1]
| Instar | Color/ Description | Body length | Hind femur | Antennal segment number |
|---|---|---|---|---|
| Eggs | Tan | 4.8 to 5.2 mm | ||
| 1 | Dark brown vertical stripe below compound eye and horizontal band behind compound eye; hind femur and medial area almost wholly fuscous | 4.8-6.2 mm | 3-3.2 mm | 12-13 |
| 2 | Green head color; vertical ivory band below compound eye; hind femur and medial area almost wholly fuscous; generally green or sometimes tan | 6.8-7.5 mm | 4-4.4 mm | 15-16 |
| 3 | Green head color; vertical ivory band below compound eye; hind femur and medial area almost wholly fuscous; generally green or sometimes tan | 8-9.1 mm | 5.2-5.4 mm | 18-19 |
| 4 | Green head color; vertical ivory band below compound eye; partly green hind femur; generally green or sometimes tan | 10.7-12 mm | 7-7.6 mm | 21-22 |
| 5 | Green head color; vertical ivory band below compound eye; partly green hind femur; generally green or sometimes tan | 14.5-18.5 mm | 9.3-10.2 mm | 23 |
| Adult Males | Live weight: 110mg
Dry weight: 35mg |
14.5-15 mm | 9.3-9.9 mm | 22-24 |
| Adult females | Live weight: 300mg
Dry weight: 90mg |
18.5-21.5 mm | 11-13 mm | 23-24 |
Identification resources
Distribution
The four-spotted grasshopper is broadly distributed across the western Great Plains from Canada prairies to central Mexico.[2] Although these individuals have been rare in Alberta and Saskatchewan, their populations in these regions have been increasing in recent years.[3]
Biology
Four-spotted grasshoppers produce one generation annually. Considered part of the intermediate hatching group, the hatching lasts for two to three weeks. Adults are found from July to September in most regions [2] and generally remain in the locations they were hatched.[1] Copulation begins with males chasing females, drawn by their movement. The female stops movement to signal copulation, and males begin by tipping their hind femora and stridulating. Females can reject the males mounted on them, as they are able to stridulate by shaking their hind femora in a vertical position. Females oviposit in the soil, laying a clutch of 6 to 14 eggs within an egg pod.[1]
Habitat and Ecology
The four-spotted grasshopper occupies shortgrass, mixed grass, desert, and bunchgrass prairie ecosystems. This species almost exclusively feed on grasses, with 89 to 100 percent of their diet consisting of blue grama for adults and nymphs. Individuals feed on green leaves by either climbing onto the plant and feeding on it about one inch below the tip, working their way down or sitting diagonally to the plant and feeding on the ends of the leaf and working their way towards the base. This type of feeding method produces plant litter which exacerbates competition with rangeland livestock.[1]
The four-spotted grasshopper is a ground-dwelling species. At night, both nymphs and adults rest lying flat on small patches of bare soil or plant litter, typically bordered by blue grama and threadleaf or needleleaf sedge. One to two hours after sunrise, grasshoppers bask by positioning their bodies sideways to the sun. As temperatures rise above 70°F, they become active, feeding, mating, and moving until it gets too hot. When the soil surface temperature reaches around 100°F, grasshoppers lying flat on bare ground shift into a stilt posture, lifting their bodies as high as their legs allow. As temperatures climb further, reaching 120°F, they move up above the ground onto plants and orient themselves toward the sun. This behavior helps them avoid the heat of the ground while minimizing the amount of body surface exposed to direct sunlight; they may also spread their hind legs to aid in cooling.[1]
| Habitats | Food Sources | Environmental conditions |
|---|---|---|
| Shortgrass; mixed grass desert; bunchgrass prairies
Occupies patches of short grass in mixed grass prairie biomes Rarely inhabits tallgrass prairies |
Prefers: Blue grama; buffalograss
Other grasses: needle and thread; western wheatgrass; sand dropseed; sideoats grama; prairie sandreed |
Land-Use Change
The four-spotted grasshopper is not a long-distance flyer. Their evasive flights extend to 2.5 to 5 feet in distance and can reach 6 inches off the ground. They fly straight and silently, landing to face away from the threat. Evidence that this species occasionally disperses comes from observations in a mixed-grass prairie in eastern Wyoming, where it once reached a density of 7 nymphs per square yard. In 1970, an insecticide treatment over 840 acres nearly eradicated the local population. The species did not reappear until 1973, when a single female was found, followed by two nymphs the next year. These findings suggest the population was able to reestablish itself through dispersal and gradually began to recover. [1]
Pest status
This species is generally a subdominant in rangeland areas. When the species is dominant, densities can range up to 5 young adults per square yard [1] The four-spotted grasshopper does not readily feed on carbaryl bait. [4]
Parasitism may be a particularly significant cause of mortality for four-spotted grasshoppers. These parasites more frequently attack adults, than nymphs in various stages of development. Seasonal parasitism may occur from July to September, when nymphs are far into their development or when adults start to occur. Natural predators of parasites that threaten grasshopper species include predatory asilids and spiders. These organisms, along with weather conditions, help maintain parasitism and in turn grasshopper parasitism. [5]
Outbreaks
In 1955, there was a major grasshopper outbreak in western Oklahoma rangeland where P. quadrimaculatum was one of the dominant species along with Ageneotettix deorum, Aulocara elliotti, Boopedon nubilum. [1]
In 1956, P. quadrimaculatum was one of the dominant species during a grasshopper irruption on the desert prairie of San Rafael Valley, Arizona. Alongside several other species, it contributed to significant grass forage loss across the affected area. [1]
Outbreak media coverage
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Associated organizations
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Resources
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 Pfadt RE (2002) Field guide to common western grasshoppers. Wyoming Agricultural Experiment Station Bulletin 912, 1–80. https://hopperwiki.org/images/d/db/Field_Guide_to_Common_Western_Grasshoppers.pdf
- ↑ 2.0 2.1 2.2 2.3 2.4 Capinera JL, Scott RD, Walker TJ (2005) Field guide to grasshoppers, katydids, and crickets of the United States. Cornell University Press, Ithaca, New York, 280 pp.
- ↑ 3.0 3.1 Johnson DL (2003) Slant-faced grasshoppers of the Canadian Prairies and Northern Great Plains. Arthropods of Canadian Grasslands 9: 5–16. Biological Survey of Canada, Ottawa. https://www.ars.usda.gov/ARSUserFiles/30320505/grasshopper/ID%20Tools/naturalist%20guides/sltgh.pdf
- ↑ U.S. Department of Agriculture (2000) What, when, and where do grasshoppers eat? In: Grasshopper Integrated Pest Management User Handbook. Technical Bulletin No. 1809. USDA Agricultural Research Service, Sidney, MT. Section II.13: 1–4. https://www.ars.usda.gov/ARSUserFiles/30320505/grasshopper/Extras/PDFs/IPM%20Handbook/II13.pdf
- ↑ Przybyszewski J, Capinera JL (1991) Patterns of parasitism among shortgrass prairie grasshopper (Orthoptera: Acrididae) populations. Journal of the Kansas Entomological Society 64(1): 5–17. https://www.jstor.org/stable/25085239