Gryllotalpa orientalis
| Gryllotalpa orientalis | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Orthoptera |
| Suborder: | Ensifera |
| Family: | Gryllotalpidae |
| Genus: | Gryllotalpa |
| Species: | G. orientalis |
| Binomial name | |
| Gryllotalpa orientalis Burmeister, 1838 | |
| Synonyms | |
|
Gryllotalpa fossor Scudder, 1869 | |
Gryllotalpa orientalis is a species of mole cricket in the family Gryllotalpidae, commonly known as the oriental mole cricket. It is found in much of Asia and also in Australasia. At one time this species was misidentified as G. africana and thought to have a widespread distribution in both Africa and Asia but in the 1980s, G. orientalis was recognised as a separate species.[1] It is a polyphagous pest, damaging crops by gnawing their roots.[2]
Morphology and biology
This mole cricket is plump, yellowish-brown, paler beneath and about thirty millimetres long. It has short filiform antennae, forelegs designed for digging and a large oblong pronotum. The wings project slightly from beneath the forewings. After mating underground, the female builds a nesting chamber deep in the soil and lays about two hundred oval eggs which hatch after ten days. The nymphs remain in their nest for the first two or three weeks, guarded by the female.[2] A newly hatched nymph has a blueish-white prothorax and legs. Later instars are grayish-black with white markings and the last nymphal stage is similar to the adult and exhibits short wing pads.[3] The whole life cycle lasts for one to three years depending on the climatic conditions. The adults and later instar nymphs spend the winter underground at a depth of about a metre.[2]
Distribution
The oriental mole cricket is found in Russia and other parts of the former USSR, China, Japan, Taiwan, India, Indonesia, Australia, the Philippines [2] and Hawaii, where it seems to have arrived from Asia before 1896.[1]
Ecology
The oriental mole cricket lives underground in damp soil, digging a network of passages. Its natural habitat include damp rich soils such as flood plains and the banks of streams and ponds as well as arable land and gardens.[2] The burrow has vertical and horizontal passages and may be complex in structure, with different parts being used for different purposes.[4] The mole cricket feeds on the roots of plants, tubers and rhizomes and also on insects, earthworms and other invertebrates. It comes to the surface and undertakes flight in the evenings and at night and is attracted to light sources. A mass emergence after wintering may take place when the temperature rises to 12-15 °C. Besides birds and insectivorous mammals, its natural enemies include ants which feed on the eggs, beetles which eat the larvae, nematodes and mites. Fungal diseases may be devastating during winters with sudden rises of temperature and thaws.[2]
Economic significance
In Hawaii, sugarcane crops have been attacked by this cricket and its tunneling activities have caused damage to the banks of irrigation ditches.[1] In Asia, the cricket gnaws roots and tubers and causes damage to wheat, barley, oats, rice, maize, beans, vegetable crops, potatoes and sugar beet. Measures to control the pest include deep ploughing, trapping, soil fumigation, poison baits and the application of insecticides.[2] In Australia there are a number of host plants and damage is sometimes done to rice crops in raised nursery beds or in upland conditions. In wetland rice, the crickets can be seen swimming between plants.[3]
Biological control in Hawaii
Larra is a genus of wasps in the family Crabronidae the members of which are parasitoids of mole crickets. After several unsuccessful attempts to introduce these wasps to Hawaii, in 1925, Larra polita from the Philippines was successfully introduced and succeeded in establishing itself. There has been little comment since 1930 on the damage being done by the oriental mole cricket in Hawaii and there is speculation that this may be due to the presence of these wasps.[1]