Orthoptera (grasshoppers, crickets and locusts): what characterizes them?

Orthoptera… The term speaks for itself because it is composed of the Greek orthos which means “right”, and pteron which means “wing”. Orthoptera are therefore insects with straight wings. But non-specialists will no doubt wonder what this means exactly. Orthoptera constitute a homogeneous group of nearly 20,000 species, of which 220 are found in France, of which a little less than half are locusts. Here are our explanations and details on what precisely characterizes these animals.

Characteristic n ° 1: the head

To describe an orthopteran, we divide the animal into three parts, as is the case with all insects: head, thorax and abdomen.

The head is said “orthognate”, Ie the axis of the preoral space is perpendicular to the axis of the body. She wears :

  • A pair of antennas,
  • Eyes, generally large in proportion to the body,
  • Powerful mandibles,
  • And palps.

The head is large and rounded with a vertical face.

The antennae are moniliform, that is to say that when observed under a microscope, they present a succession of constrictions and swellings, which gives them the appearance of a pearl necklace. These antennas can be short or very long. In locusts they are thick and shorter than their bodies, while in grasshoppers and crickets they are thin and long.

Like most insects, Orthoptera have mouth parts clearly visible from the outside: they are said to be “ectognaths”.

The mouthparts are grinder-type and feature powerful mandibles.

Characteristic n ° 2: the thorax

The body of Orthoptera is robust and varying in length between 5 mm and 15 cm. The prothorax is covered with a shield (or pronotum).

The thorax has two pairs of wings. The wings are called “straight” because they are folded along the back of the insect when it is posed. “Tegmina” (the singular is “tegmen”) is the term for the fore wings of orthoptera, visible in adults when posed. Equivalent to the “elytra” of beetles, these are hard wings, which do not participate in the flight but cover the other pair of wings, folded below like a fan.

Wing length varies by species, and can be either longer than the body or smaller and leaving part of the abdomen visible. Orthoptera are also said to be “exopterygotes”, That is, their wings develop outside their body.

The thorax also has three pairs of legs (anterior, median and posterior). The hind legs are long, suitable for jumping. They have very large and sturdy femurs. Unlike grasshoppers, crickets’ hind legs are set apart from the rest of the body and are never green in color – a good way to distinguish these animals from each other.

Feature # 3: the abdomen

The terminal part of the abdomen is cylindrical and presents more or less long cerci, and genitals which are partially hidden in the male but are, on the contrary, clearly visible in the females.

Mating takes place a few days or weeks after the last moult, and spawning only a few days later after mating. Grasshoppers have an organ called ovipositor which allows them to deposit the eggs deep in the soil. Other species lay eggs in cracks in bark or in plants rich in pith. Egg development can sometimes take several years.

Characteristic n ° 4: chirping

Orthoptera emit characteristic sounds called chirping. The functions of this “song” are varied and differ according to the species: attraction of the female by the male to form a couple and reproduce, marking of the territory or defense.

In most grasshoppers and crickets, only males make these sounds and do so by rubbing their wings together. In this case, the left tegmen has a rasp called a “stridulatory crest” and the right, a scraper called a “bow” as well as a resonant surface called a “mirror”. It happens differently with locusts which rub their hind legs against their wings.

Characteristic n ° 5: an incomplete metamorphosis

Orthoptera undergo a metamorphosis in three stages, egg, larva, imago.

But they are said “hemimetabolous”, A term which means that the metamorphosis is incomplete: the larvae and nymphs resemble adults, except that the wings and genitals are not formed.

The diet and method of eating are also often the same as for adults. Most orthoptera are phytophagous: all locusts are, but it is more variable in grasshoppers and crickets, whose diet can also be carnivorous.

Protect Orthoptera

Extensive grazing and regular mowing are favorable to the protection of orthoptera. But determining the best time to mow must be done locally as it varies between species. For those who lay their eggs in the ground, do not mow between May and August. For those who lay eggs on or in plants, mowing before May and after August is unfavorable.

In addition, here are some recommendations that promote the preservation of orthoptera:

  • Minimize the number of mows to approach one per year,
  • Differentiate between maintenance to maintain different shelter belts,
  • Cut to at least 10 cm,
  • Favor the use of the scythe,
  • Let the hay dry in place.