Dociostaurus maroccanus
Encyclopedia
Dociostaurus maroccanus, commonly known as the Moroccan locust, is a grasshopper
in the insect
family Acrididae
. It is found in northern Africa, southern and eastern Europe and western Asia. It lives a solitary existence but in some years numbers increase sharply, it becomes gregarious and congregates to form swarms which can cause devastation in agricultural areas.
("hoppers") resemble wingless adults. They moult five times, each instar
having larger wing pads. The adult female locust is 20 to 38 millimetres long and the male 16 to 28 millimetres long. The body colour is yellowish gray with dark patches. There is a creamy coloured cross-shape on the prothorax
. The elytra
are large and transparent, sometimes speckled with brown, and the wings are colourless and strongly veined. The hind legs are powerful, the femur
often being banded with black while the tibia
is usually red. The time taken from hatching to maturity is about thirty days.
This locust has traditionally been considered a serious agricultural threat. Its large numbers, voracious appetite, ability to eat almost all forms of vegetation and ability to migrate in swarms make it a feared pest. However, outbreaks of swarming activity have diminished in recent years and in some areas the Moroccan locust has become rare. This is particularly noticeable in European countries where the species no longer seems to be an economic threat while in north Africa and parts of central Asia it still flourishes. These alterations in population dynamics may be due to a change in climatic conditions with a decrease in spring rainfall. A more important factor may be the increase of cropland at the expense of grassland, since the female needs undisturbed soil in which to deposit her eggs. At the other extreme, overgrazing and deforestation in some areas provide a favourable environment for the species to thrive and remain destructive.
In a study in Iran in 1956 it was found that outbreaks of locusts originated from just eight distinct areas. All these districts were in mountain foothills that had been forested or in other rolling foothills. In all cases the vegetation consisted of annual grasses or shrub steppe
communities with annual grasses and dwarf shrubs. There was a good supply of green food in winter which increased the longevity and fertility of the females. Outside these districts, the Moroccan locust had solitary populations whereas inside them, in some years, the locust became gregarious. The locust needs firm, bare soil for egg laying and when they hatch, the nymphs move to progressively taller and more dense vegetation. These districts principally had rainfall in winter and early spring, averaging 250 to 350 millimetres. The temperature averaged about 17°C in the months immediately before and after egg laying. The sites were heavily grazed by sheep and goats, especially in winter. The conclusion of the study was that quite specific climate, vegetation, and topographical conditions were needed for breeding to take place.
Grasshopper
The grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as the short-horned grasshopper...
in the insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
family Acrididae
Acrididae
The Acrididae are the predominant family of grasshoppers, comprising some 10,000 of the 11,000 species of the entire suborder Caelifera. The Acrididae are best known because all locusts are of the Acrididae. The subfamily Oedipodinae is sometimes classified as a distinct family Oedipodidae in the...
. It is found in northern Africa, southern and eastern Europe and western Asia. It lives a solitary existence but in some years numbers increase sharply, it becomes gregarious and congregates to form swarms which can cause devastation in agricultural areas.
Distribution
The range of the Moroccan locust extends from the Canary Islands and Madeira in the west to Kazakhstan and Afghanistan in the east. In Africa it is found in Algeria, Egypt, Libya, Morocco and Tunisia. In Europe it is found in France, Portugal, Spain, Italy and the Balkan peninsula. It is also found in the Middle East and Central Asia.Description
The eggs are laid in pods with about thirty eggs each. The nymphsNymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
("hoppers") resemble wingless adults. They moult five times, each instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
having larger wing pads. The adult female locust is 20 to 38 millimetres long and the male 16 to 28 millimetres long. The body colour is yellowish gray with dark patches. There is a creamy coloured cross-shape on the prothorax
Prothorax
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites are the pronotum , the prosternum , and the propleuron on each side. The prothorax never bears wings in extant insects, though some fossil groups possessed...
. The elytra
Elytron
An elytron is a modified, hardened forewing of certain insect orders, notably beetles and a few of the true bugs ; in most true bugs, the forewings are instead called hemelytra, as only the basal half is thickened while the apex is membranous...
are large and transparent, sometimes speckled with brown, and the wings are colourless and strongly veined. The hind legs are powerful, the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
often being banded with black while the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
is usually red. The time taken from hatching to maturity is about thirty days.
Ecology
The Moroccan locust lives in arid areas between 500 and 1000 metres above sea level. It breeds in undisturbed soil and does not reproduce in arable fields. The optimum rainfall for development in the months from March to May is one hundred millimetres. If the spring is unusually hot and precipitation is low, and especially if it is the second dry spring in succession, numbers of young locusts can increase dramatically. Mass outbreaks of nymphs occur and destroy the vegetation where they hatch. From the second instar stage onwards, the hoppers aggregate and the population density can reach several thousand nymphs per square metre. The hoppers move downhill to fertile regions damaging crops as they go. Multiple generations can be present, and the numbers of adults can build up rapidly, reaching 300 individuals per square metre in extreme cases. Winged adults take flight en masse at low altitudes, travelling at eight to ten metres per second and may migrate sixty kilometres during the season. Numbers begin to diminish in June when the vegetation is also declining.This locust has traditionally been considered a serious agricultural threat. Its large numbers, voracious appetite, ability to eat almost all forms of vegetation and ability to migrate in swarms make it a feared pest. However, outbreaks of swarming activity have diminished in recent years and in some areas the Moroccan locust has become rare. This is particularly noticeable in European countries where the species no longer seems to be an economic threat while in north Africa and parts of central Asia it still flourishes. These alterations in population dynamics may be due to a change in climatic conditions with a decrease in spring rainfall. A more important factor may be the increase of cropland at the expense of grassland, since the female needs undisturbed soil in which to deposit her eggs. At the other extreme, overgrazing and deforestation in some areas provide a favourable environment for the species to thrive and remain destructive.
In a study in Iran in 1956 it was found that outbreaks of locusts originated from just eight distinct areas. All these districts were in mountain foothills that had been forested or in other rolling foothills. In all cases the vegetation consisted of annual grasses or shrub steppe
Shrub-steppe
Shrub-steppe is a type of low rainfall natural grassland. Shrub-steppes are distinguishable from deserts, which are too dry to support a noticeable cover of perennial grasses or other shrubs, while the shrub-steppe has sufficient moisture levels to support a cover of perennial grasses and/or...
communities with annual grasses and dwarf shrubs. There was a good supply of green food in winter which increased the longevity and fertility of the females. Outside these districts, the Moroccan locust had solitary populations whereas inside them, in some years, the locust became gregarious. The locust needs firm, bare soil for egg laying and when they hatch, the nymphs move to progressively taller and more dense vegetation. These districts principally had rainfall in winter and early spring, averaging 250 to 350 millimetres. The temperature averaged about 17°C in the months immediately before and after egg laying. The sites were heavily grazed by sheep and goats, especially in winter. The conclusion of the study was that quite specific climate, vegetation, and topographical conditions were needed for breeding to take place.