Melanoplus propinquus Scudder Orthoptera Acrididae

Natural History

Distribution. The redlegged grasshopper, Melanoplus femurrubrum (De Geer), is known from nearly all of the United States and southern Canada, and its distribution also extends south through most of Mexico. In parts of the southeast, on the coastal plain from eastern North Carolina to southern Mississippi and Louisiana, and including all of Florida, it is replaced by a very similar form, M. propinquus Scudder, which appears to be a separate species (Dakin, 1985). These are native insects.

Host Plants. These species are polyphagous, feeding on a broad range of plants and apparently preferring a dietary mixture over a single food plant, and broadleaf plants over grasses. The preferred habitat is tall vegetation in pastures, fence rows, along irrigation ditches and roadways, and in fallow agricultural fields which have become weedy. The redlegged grasshoppers are known throughout North America for damage to crops, attacking alfalfa, barley, birdsfoot trefoil, clover, corn, lespedeza, oat, orchardgrass, soybean, timothy, tobacco, and vetch in addition to vegetables. Among vegetable crops, bean, beet, cabbage, and potato seem to be most frequently injured, but nearly any crop may be fed upon. Among the uncultivated plants eaten are aster, Aster spp.; Kentucky blue-grass, Poa pratensis; brown knapweed, Centaurea jacea; cinquefoil, Potentilla argentea; dandelion, Taraxacum officinale; fleabane, Erigeron divergens; goldenrod, Soli-dago canadensis; kochia, Kochia scoparia; Russian thistle, Salsola kali; smooth brome, Bromus inermis; sweet clover, Melilotus officinalis; wavyleaf thistle, Cirsium undu-latum; western ragweed, Ambrosia psilostachya; and likely many others. The weeds fed upon most frequently in North Dakota alfalfa fields were reported to be kochia, Kochia scoparia, field bindweed, Convolvulus arvensis; awnless bromegrass, Bromis inermis; and foxtail, Setaria spp. (Mulkern et al., 1962). On prairie, redlegged grasshopper ate primarily Kentucky blue-grass, Poa pratensis; western ragweed, Ambrosia psilos-tachya; golden aster, Chrysopsis villosa; flixweed, Descurainia sophia; and leadplant, Amorpha canesens (Mulkern et al., 1964). Bailey and Mukerji (1976) were able to culture redlegged grasshopper on nearly all plants tested, though they completed development more rapidly when provided with plants on which they preferred to feed.

Natural Enemies. The natural enemies of the crop-feeding Melanoplus spp. are quite similar. For information on natural enemies of redlegged grasshopper, see the section on natural enemies of migratory grasshopper, Melanoplus sanguinipes (Fabricius).

Weather. Like most grasshoppers, redlegged grasshopper is favored by hot weather. Long-term periods of drought and hot weather favor population increase, especially in northern areas that normally are cooler. A certain amount of precipitation is necessary to provide adequate food for the grasshoppers, of course, but prolonged cool, wet weather, especially during the period of eggs hatch, is detrimental for survival. The late onset of winter can favor grasshopper population increase because it allows adults additional time to produce eggs.

Life Cycle and Description. There is only a single generation per year throughout the range of these species, with the egg stage overwintering. Eggs hatch in late spring and adults are present from July until they are killed by heavy frost, though their numbers decrease steadily throughout the season. The follow ing information has been derived from studies of M. femurrubrum, but likely applies equally well to M. propinquus.

  1. The eggs are elongate-cylindrical, and widest at the middle. They measure 4.1-4.6 mm long and 0.91.5 mm in diameter. Their color is yellowish-brown or creamy-white. They are deposited in structures called pods, which consist of two columns of eggs arranged in parallel rows. The pod, which is secreted by the female during oviposition, consists of frothy material secreted between, and covering, the eggs. The pod is a curved cylinder in form, and measures about 2025 mm long and 3-5 mm in diameter. It is buried in the soil, and normally contains 20-26 eggs per pod. The upper portion of the pod consists solely of froth, and the young grasshoppers chew their way through this material to escape from the soil. Eggs are often deposited among the roots of grasses and weeds, particularly along the edges of crop fields. Females can produce 300 eggs during their life time. These are not early season grasshoppers. Hatching occurs about three weeks after hatching of twostriped grasshopper, Melanoplus bivittatus (Say), two weeks after migratory grasshopper, Melanoplus sanguinipes (Fabricius), and about the same time as differential grasshopper, Mela-noplus differentialis (Thomas), with which redlegged grasshopper may co-occur. The period of hatching is extended, however, so nymphs can be found during most of the summer.
  2. Development of the nymphal stage normally requires about 40 days, during which there usually are 5-6 instars. Throughout their development they are yellowish, but marked with a broad black stripe that extends across the face, eyes and prothorax, and onto the abdomen. They also bear a second, less discrete black stripe that is below, but parallel to the aforementioned stripe, and that arches across the lateral lobe of the prothorax. The outer face of the femora is marked with a broad black stripe. The underside is yellowish. The hind tibiae are yellow or gray, and bear black spines. The overall body length of nymphs is 4.0-5.6, 6.2-7.2, 7.4-9.7, 10.0-15.5, and 16.5-22.5 mm for instars 1-5, respectively. Antennal segment numbers increase from 12-14 to 15-16, 17-19, 22-24, and 24-26 in the corresponding instars. Bellinger and Pien-kowski (1989) reported mostly 6-7 instars in Virginia. They reported total nymphal development times for grasshoppers displaying a total of six instars to average 67, 42, 31, and 29 days when cultured at 26.5°, 30°, 35°, and 38°C, respectively. Nymphs developing through seven instars required 5-10 additional days, depending on the rearing temperature. Mean instar development time was reported to be 3.6, 4.1, 4.7, 5.0, 5.8, and 7.9 days for instars 1-6 when cultured at 35°C, an optimal temperature. Nymphs change their behavior in response to temperature, with feeding commencing at 20-24° C, and nymphs moving to elevated perches to escape the heat when the air or soil temperatures get high. Like most grasshoppers, they tend to remain inactive, even at high temperature, in the absence of sunlight.
  3. The adults are medium-sized grasshoppers, the males measuring 17-23 mm long, and the females 18-27 mm. They are reddish-brown or grayish-brown dorsally and yellow or yellowish-green ventrally. The front wings lack distinct markings; the hind wings are colorless. The lateral lobe of the prono-tum is usually marked with a distinct black area. The outer face of the hind femora are yellowish but bear an indistinct dark stripe. The hind tibiae are almost always deep red with black spines, and are the basis for the common name of these grasshoppers. In the male, the tip of the abdomen is rather bulbous, with the subgenital plate bearing a broad "U"-shaped depression apically. The cerci narrow rapidly from the base, with the distal third narrow and the tip either angled (M. femurrubrum) or rounded (M. propinquus).

The males, but not the females, of these two species are easily separated by the genitalia. In M. femurrubrum, the cerci are pointed at the tip, formed by an acute angle. The cerci at the mid-point are relatively broad, about one-half the maximum width at the base. The furcula in this species diverge from the base and then converge distally, the space between the arms of the furcula forms a "U" shape. In contrast, in M. propinquus the tips of the cerci are rounded, and the cerci are relatively narrow at the mid-point, about one-third the maximum width at the base. The furcula diverge more strongly, the space between the arms forms a "V" shape (Dakin, 1985).

Adults normally roost at night on the tops of tall grasses and weeds. Early in the morning they crawl down the plant and resume feeding when the air temperature warms, often moving along the soil in search of food. As happens with nymphs, the adults ascend vegetation to escape high temperature. In the evening, they perch again on elevated roosts, and remain there until they are warmed by sunlight in the morning. Females have a pre-oviposition period of 9-15 days before they commence egg laying. Redlegged grasshopper is a fairly strong flier and can fly 10 m if disturbed. (See color figure 163.)

Despite its importance, comprehensive treatment of M. femurrubrum biology is lacking. Some important aspects were given by Parker (1939), Shotwell (1941)

Adult male redlegged grasshopper.

Male redlegged grasshopper, tip of abdomen.

and Bellinger and Pienkowski (1989). A very good synopsis was presented by Pfadt (1994d), who also pictured all stages of development. A summary of red-legged grasshopper biology, including keys to related Canadian Orthoptera, was given by Vickery and Kevan (1985). Melanoplus femurrubrum was included in many grasshopper keys, including those by Blatch-ley (1920), Dakin and Hays (1970), Helfer (1972), Capi-nera and Sechrist (1982), and Richman et al. (1993). Blatchley (1920) includes M. propinquus; and Dakin and Hays (1970) treated the two redlegged grasshoppers as subspecies. Melanoplus femurrubrum was also included in a key to grasshopper eggs by Onsager and Mulkern (1963). Rearing of Melanoplus spp. was described by Henry (1985).

Damage

Redlegged grasshopper is a defoliator, often removing all leaf tissue and leaving only plant stems. Lower densities leave plant ragged or tattered. Redlegged grasshopper is a common component of the grasshopper complex that affects plants growing along the margins of fields, though it causes extensive damage only during periods of very high density. Redlegged grasshopper is capable of developing high densities and migratory tendencies during periods of drought, and may be found mixed into swarms of migratory grasshopper, Melanoplus sanguinipes (Fabricius).

Management

Management of the various Melanoplus spp. grasshoppers is substantially the same. For information on redlegged grasshopper management, see the section on management under migratory grasshopper, Melanoplus sanguinipes (Fabricius).

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