Invertebrate Zoology: A Study Guide - T. A. Dauda 2014

Multicellular Animals
Arthropods
Subphylum Tracheata - Class Insecta - Orders with Incomplete Metamorphosis - Order Orthoptera

There are about 20,000 known species of orthopterans. These are medium to large-sized insects with a large pronotum and, frequently, very long antennae. Their tegmina (leathery forewings) are held flat over the back when at rest. The hind wings are more delicate, fold fan-like, and are sometimes reduced. Mouthparts are of the chewing type. The hind legs are typically adapted for jumping, characterized by heavily muscled femurs and very long tibiae. Females possess an ovipositor.

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Fig. 65 Representatives of the order Orthoptera:

1 — green grasshopper; 2 — mottled grasshopper; 3 — desert cricket.

Orthopterans possess Organs of Hearing. In addition, males have specialized and variously structured organs that produce loud chirping or scraping sounds. These sounds attract females during the mating season.

Orthopterans are fairly clearly divided into Tettigoniidae (long-horned grasshoppers), Gryllidae (crickets), and Acrididae (short-horned grasshoppers/locusts) (Fig. 65). In long-horned grasshoppers, the antennae are long, often extending well past the middle of the body. The tarsi are four-segmented. Appendages known as cerci are present on the abdomen. The organs of hearing are located on the tibiae of the forelegs. The stridulatory Organs of the males are situated on the forewings. A resting grasshopper makes rapid movements with them to produce sounds.

Among grasshoppers in our fauna, the dark bush-cricket and the great green bush-cricket are the most common. There are many herbivorous and omnivorous species among grasshoppers, as well as some predators. There are relatively few agricultural pests.

In crickets, the antennae are very long, usually exceeding the body length. The tarsi are three-segmented. Cerci are located at the tip of the abdomen.

Typical representatives of crickets are the field cricket and the house cricket. The mole cricket, which inhabits the soil, also belongs to this group (Fig. 66). Its forelimbs are adapted for burrowing: the tibiae are widened and lined with Teeth along the edge. Mole crickets are typically found in moist soil, in vegetable gardens, hotbeds, or sugar beet fields.

Fig. 66 Mole cricket

In the southern regions of our country, as they burrow through the soil, they occasionally damage plant roots. Thorough autumn plowing can help prevent this damage.

Acrididae (short-horned grasshoppers and locusts) include many dangerous pests of agricultural crops, especially cereals. They differ from long-horned grasshoppers by having short antennae (shorter than half the body length) and three-segmented tarsi, while their auditory organs are located on the 1st abdominal segment. Locusts produce stridulation, often resembling a scraping sound, by rubbing their Femur against the edge of the forewing. The ovipositor in female locusts is short. In most species, egg clutches are enclosed in structures called egg pods (oothecae).

Among locusts, the most dangerous pests are the gregarious forms, often simply referred to as locusts (see Fig. 60). The migratory or Asian locust can appear in enormous numbers and devastate crops over vast areas. As a mass pest, locusts are distributed primarily in the tropical and subtropical countries of the Old World. In our country, mass locust invasions have affected the southern regions adjacent to their native habitats.

Breeding grounds for the migratory locust include reed thickets along the lower reaches of rivers — the floodplains of the Don, Kuban, Terek, Ural, and other rivers. Here, females lay egg pods in the soil in autumn. Usually, a tremendous number of egg pods are concentrated in these breeding sites. Embryonic development begins in autumn but pauses for the winter; in spring, larvae hatch and molt 4 to 5, and occasionally 6 times during the summer. As they mature, they form large aggregations, known as bands or hoppers, thus transitioning to a gregarious lifestyle. Initially, the larvae feed locally, but later, in older instars, driven by the search for food, hordes of "walking" locusts begin to migrate over long distances, devouring all vegetation in their path. After the fifth molt, winged adults appear. Enormous swarms of winged locusts take to the air and can undertake long-range flights, destroying all plants wherever such a swarm lands.

Other locust species found within the territory of the former USSR include: the Moroccan locust (Crimea, Caucasus, Central Asia, southern Russia), which damages many cultivated crops, especially cotton; and the Italian locust (southern Ukraine, Crimea, Caucasus, Central Asia), which attacks mainly industrial and vegetable crops. The Siberian locust also causes significant damage.

Systematic control of locusts primarily involves destroying egg pods and early developmental stages in their breeding grounds, as well as eradicating migrating hordes. Drainage and plowing of river floodplains are of paramount importance, as they lead to the destruction of habitats suitable for locust reproduction. Thanks to such comprehensive and systematic control measures, the migratory locust has ceased to exist as a mass pest in our country.

A continuous threat is posed by incursions of locust swarms from neighboring countries — Iran, Afghanistan, and Turkey.