by: Deanna Dodgson
Above: psoloessa-delicatula---brown-spotted-grasshopper by Deanna Dodgson
Natural grasslands around the world are perilously close to extinction. By association, many animal and plant species that exist here are also threatened. Drought, flood, fire and fire suppresion, forest encroachment, habitat fragmentation and rising global temperatures lead to changes in vegetative cover, affecting species diversity as well as the balance of the insect communities found here. The grasshopper is not immune to these threats.
The grasshopper, or acridid (family Acrididae, or Short-horned Grasshoppers), is a dominant invertebrate of grasslands. In the grasslands, three sub-families are represented: Band-winged (Oedipodinae), Spur-throated (Melanoplinae), and Slant-faced (Gomphecerinae). Each is named for its physical characteristics. Band-winged grasshoppers have a more or less prominent “band” across the outer forewing surface, Spur-throated have a small ventral spur found between the forelegs, and Slant-faced have an appropriately inclined facial profile. Members from all three sub-families are found exclusively in grasslands or within the prairie/forest interface.
Some grasshopper species feed on carrion, dung or fungi. The locally rare Cudweed Grasshopper (Hypochlora alba) is unusual in that it eats Pasture Sage (Artemisia ludoviciana) almost exclusively. But most grasshoppers are generalist feeders, eating a mix of grasses and sedges and/or forbs.
Of the local grassland species, very few are serious crop pests, but that wasn’t always the case. The extinct Rocky Mountain Locust was a scourge of North American farmers in the mid to late 1800's. At their peak, they descended on the plains in numbers that darkened the skies and devastated crops, gardens and grasslands alike. The effects of the Rocky Mountain Locust were felt here in Manitoba. In some years, local farmers wouldn’t bother to plant crops, thus mitigating their losses. With the advent of management techniques, outbreaks such as these no longer occur.
Open areas are important for many grasshoppers. These areas are used for feeding, courtship, oviposition (laying eggs), basking and sleeping. Open areas also encourage soil warming, which is important for the development of eggs. Most grasshoppers overwinter as eggs, but some overwinter as partially to nearly full-grown nymphs. Grasshoppers often molt five to six times before becoming an adult, and the life-cycle of some species takes two years to complete.
The grasshopper is an important part of the grassland ecosystem. At 35 to 75% crude protein, acridids are a rich source of energy. Grassland birds like Sprague's Pipit and Chestnut-collared Longspur (both Species at Risk), rely on acridids and other invertebrates to feed their young. Depending on prey availability and preference, as much as 80% of a nestling's diet can consist of grasshoppers. Adult birds also feed on grasshoppers, and as much as one third of their diet may be composed of them.
Birds are not the only animals to exploit these insects. Mammals such as coyote, fox, raccoon, skunk, ground squirrels, mice and shrews supplement their diet with them. Grasshoppers are also hunted by toads, predatory and parasitic insects, and predatory spiders. Grasshopper eggs are attacked by larval bee flies and blister beetles, as well as ground beetles and crickets, among others.
Praririe ecosystems are shaped and maintained by diverse forces. And although grasshoppers are a great food source for several species, excessive feeding by grasshoppers can decrease plant abundance and/or reduce vegetative diversity. But Acridids can also have a positive effect on their environment. Nitrogen, which is vital to plant growth, can be quickly cycled back into the ecosystem through the decomposition of fecal matter and dead grasshoppers. When this process occurs at a greater rate than the level of feeding, plant abundance is generally encouraged.
Because grasshoppers belong to a diverse family of insects, they have great ecological and economic value on the prairies. But they are also very interesting creatures. Grasshoppers exhibit a wide range of behaviours that can be fairly easily observed – from aggressive encounters to the flamboyant courtship rituals of the Band-winged species. Some are attractively marked in bold colours, some in very subtle hues, and a few are patterned to mimic the substrates they live on. Their diversity makes them a great subject for both novice and experienced naturalists. Conserve and appreciate our grasslands, and marvel at the grasshopper too.