ORIENTAL MOLE CRICKET

Gryllotalpa orientalis Burmeister
(grill-oh-TALP-a orient-AHL-iss)

Distribution

The oriental mole cricket arrived in Hawaii, from Asia, before 1896. Hawaii is the only part of the United States where it now occurs.

Description

Initially, this immigrant mole cricket to Hawaii was misidentified as Gryllotalpa africana, the African mole cricket, but in fact it is Gryllotalpa orientalis, the oriental mole cricket.

As with other mole crickets in the genus Gryllotalpa, the tibia of the oriental mole cricket has four dactyls. There is a row of five spines on the upper margin of the tibia of each hind leg. This characteristic is shared by the western and European mole crickets, but not by the prairie mole cricket.

In the oriental mole cricket, the ocelli are elliptical, and the ocellar-ocular distance is less than the ocellar length. This is also true in the western mole cricket. However, in the western mole cricket the inter-ocellar distance is less than the ocellar length, whereas in the oriental mole cricket the inter-ocellar distance is greater than the ocellar length.

In the European mole cricket the ocelli are nearly circular, and the ocellar-ocular distance is greater than the ocellar length.

Life Cycle

Very little is known about the life cycle of the oriental mole cricket in Hawaii. This may be because it was misidentified as G. africana, a species which was for many years thought to have a widespread distribution in Africa and Asia, but in the 1980s was found to be restricted to Africa, whereas the origin of the mole cricket found in Hawaii is believed to be Asia, not Africa. Mole crickets from many Asian countries and Australia have likewise been misidentified as G. africana, and information on life cycles and seasonality has been published under this name. While it is likely that most of the information published on mole crickets in these other countries is accurate, it may not be applicable to climatic conditions in Hawaii, and some of it may be applicable to species other than G. orientalis. Much of the information on the oriental mole cricket in Hawaii concerns the damage that it caused to sugarcane from the time of its immigration there in the late 19th century until the 1930s.

Life-cycles of this and other species are contrasted in this knowledgebase with that of the tawny mole cricket, because it is the best-studied species.

Damage

The oriental mole cricket has been recorded as damaging irrigation dikes (by tunnelling) and sugarcane. Its status in Hawaiian turf needs clarification.

Biological Control Agents

Larra is a genus of crabronid wasps, with species occurring naturally in several continents. As far as is known, all Larra species are parasitoids of mole crickets. Hawaiian entomologists seem to have been the first to recognize the potential use of Larra in classical biological control. Faced with problems caused in Hawaii by an immigrant species of mole cricket, now believed to be Gryllotalpa orientalis, these entomologists tried to introduce Larra species. The first attempt, with Larra amplipennis from the Philippines in 1921, was unsuccessful. The second attempt, with Larra bicolor from Brazil in 1924, also was unsuccessful. But the third attempt, with Larra polita from the Philippines in 1925, succeeded in getting a population of this wasp established. Little has been written about mole cricket damage in Hawaii since the 1930s, and some have assumed that current unimportance of mole crickets in Hawaii is due to the beneficial effects of Larra polita.


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