|scientific name Melanoplus dawsoni |
common name Dawson grasshopper
The Dawson grasshopper inhabits mixed-grass prairies and in high altitude grass-forb parks or ravines in lower altitudes (Pfadt 2002).
Melanoplus dawsoni nymphs (no wings or very short wing buds) usually hatch in June through the beginning of July, although the exact timing seems to be affected by altitude. Adults (short or long wings) usually begin to appear in July, about 21 to 66 days after nymphs have hatched, and continue to emerge into August (Pfadt 2002). In Alberta, they have been found in July and August (Stickland Museum records).
The Melanoplus dawsoni is a small spurthroated grasshopper often found with very short wings, but occasionally with wings that extend past the length the abdomen. This and other grasshoppers of the subfamily Melanoplinae often have a spiny bump on their "throat" between their front legs (Johnson 2002). Adults have distinctive black and yellow ringed abdominal terga, canary yellow venter, and red hind tibia. The male cerci are short, rounded and slightly concave apically (Pfadt 2002).
The life cycle of this species is described in Pfadt's Field Guide to Common Western Grasshoppers (2002). Development from nymph, through the 5 instars, to adult is faster at higher altitudes and warmer temperatures. High altitude populations are hypothesized to have adapted physiologically to the shorter seasons and so have a shorter development time. Grasshoppers of these populations also make behavioural adjustments to maximize their heat intake by basking longer in the sun and remaining in thermal shelters longer. Mature males will stridulate to attract receptive females. Females often bore into the ground several times before actually depositing eggs. The egg pods of this species are about 2 cm long, slightly curved, and contain 8-14 tannish yellow eggs.
This grasshopper is a frequent pest of alfalfa fields (Pfadt 2002).
This grasshopper prefers to eat forbs including dandelion, common yarrow, golden aster, western ragweed, leadplant, milkvetches, alfalfa, and white clover (Pfadt 2002). It will also eat both the leaves and seeds of grasses including Kentucky bluegrass and brome grass.
The Dawson grasshopper is found across the middle of North America. From the south-east corner of British Columbia it ranges south through the Great Plains and east across the Great Lakes and up the St. Lawrence River basin (based on range map in Pfadt 2002). This grasshopper has been found in mid and southern Alberta (Strickland Museum records).
Melanoplus dawsoni adults are usually short-winged, but a few do possess long wings and can disperse effectively. One of the longest dispersals measured was of a female found 22.5 km from the nearest resident population (Pfadt 2002).
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