Montana Field Guide

The following comes from Hebard (1928), Brooks (1958), Helfer (1971), Otte (1981), Capinera and Sechrist (1982), Vickery and Kevan (1985), McDaniel (1987), Pfadt (2002), Capinera et al. (2004), and Scott (2010). A medium-sized grasshopper usually with a gray body and dark markings. The dorsal surface of the pronotum possesses a light or weak “X” marking, but other patterns often exist within a population. Hind tibia is blue.

Overwinters in the egg stage. Nymphs appear in mid-spring. Adults occur from June through September, or until the first heavy frost (Capinera et al. 2004, Capinera and Sechrist 1982, Otte 1984, Pfadt 2002, Schell et al. 2005, Scott 2010, and Vickery and Kevan 1985).

The following is taken from Hebard (1928), Brooks (1958), Helfer (1971), Otte (1981), Capinera and Sechrist (1982), Vickery and Kevan (1985), McDaniel (1987), Pfadt (2002), Capinera et al. (2004), and Scott (2010). The body length to end of forewings for males is 16 to 25 mm, and for females 22 to 35 mm. Hind femur has black bars on the outer upper area which continue onto the upper surface and onto the upper area of the inner face. The shape of the female 8th ventral segment’s posterior margin has a small bump without deep clefts.

The Big-headed Grasshopper is similar to the White-crossed Grasshopper (Aulocara femoratum). A quick separation can be made by comparing the shapes of the female 8th ventral segment’s posterior margins. A. femoratum has deep clefts. See that species for other diagnostic characters.

Favors shortgrass prairies, especially areas with sparse vegetation and bare ground (Capinera and Sechrist 1982, Capinera et al. 2004, Otte 1984, Pfadt 2002, and Vickery and Kevan 1985).

The Big-headed Grasshopper feeds mainly on grasses and sedges (2 species of sedges and 22 species of grasses), preferring bluegrass, blue gramma (Bouteloua gracilis), needle-and-thread (Stipa comata), western wheatgrass (Elymus smithii), and cheatgrass (Bromus tectorum). Rarely feeds on forbs, but will scavenge litter, seeds, manure and dead insects (Capinera and Sechrist 1982, Otte 1984, Pfadt 2002, Schell et al. 2005, and Vickery and Kevan 1985).

Pair formation and courtship consists of visual cues. Males display themselves by hind femora tipping and antennae waving. When male mounts and makes genital contact, copulation lasts for 40 to 70 minutes. Females deposit their first eggs when they are 12 to 20 days old. Seven to nine eggs are laid in a hard, smooth, foam-like pod in the top half inch of bare soil. Hatching nymphs pass through 5 instars and usually takes 36 to 42 days to reach the adult stage (Capinera et al. 2004, Capinera and Sechrist 1982, Otte 1984, Pfadt 2002, Schell et al. 2005, and Vickery and Kevan 1985).

The Big-headed Grasshopper is often the dominant species in outbreaks on rangelands. High population densities destroy the value of rangeland for grazing and can even lay the land bare. Such high densities have been observed persisting for more than five years (Pfadt 2002, Schell et al. 2005).