Members of this genus have two blade-like claws (dactyls) on each foretibia and the auditory tympanum is exposed. The foretrochanter is armed with an elongate blade. The hindtibia has 3-6 long spines along its upper inner margin.
Our three species in this genus are native to South America and first became established in North America more than 90 years ago, apparently from stowaways in ships' ballast. Maps of when and where they were introduced and how they spread are on the species pages and in Walker & Nickle (1981).
Life cycles
Two-clawed mole crickets require a year or less for a generation. In the colder parts of their ranges they overwinter both as adults and large nymphs. Eggs are laid in clutches of 25 to 60 in small ovoid chambers (4 x 3 cm) 9 to 30 cm below the surface.
Economic importance
Members of this genus are the most damaging crickets in the New World. In the southeastern United States tawny mole crickets (S. vicinus) are major pests of established lawns and pastures, causing annual losses of $10's of millions. Short-winged mole crickets (S. abbreviatus) do the same type of damage but are much more restricted geographically. Southern mole crickets (S. borellii) feed largely on animal matter and avoid established turf; however, they damage seedlings in newly planted lawns, gardens, and fields.
Biological control
Because our pest mole crickets were introduced and occurred in much greater numbers here than in their homeland, University of Florida researchers concluded that they might be controlled by classical biological control--that is, by introducing natural enemies that had been left behind when they immigrated from South America. Of the enemies that proved promising because of their host specificity, three have been successfully introduced, and have substantially reduced Scapteriscus populations. Steinernema scapterisci is a nematode that kills mole crickets by introducing lethal microbes (Parkman et al 1993). Ormia depleta is a tachinid fly that homes on the calling songs of male mole crickets and deposits living larvae that enter and consume mole crickets (Frank et al 1996). Larra bicolor is a sphecid wasp that chases a mole cricket from its burrow, subdues it with a sting and glues an egg at the base of a middle leg. The mole cricket recovers but the egg becomes a larva that feeds on the cricket while attached externally and eventually kills its host and consumes the remains (Walker 1984).
Flights
Large numbers of tawny and southern mole crickets fly during the early evening of warm days each spring. One result of such flights is that new lawns and fields are infested and pesticide-treated ones are re-infested. Another result is that females find mates by homing to the appropriate calling song and landing near the entrance to the caller's burrow.
Some important features of the flights are not adequately understood. Males and mated females, as well as virgin females, often terminate their flights by homing to conspecific calling song, and the same individual may fly and home repeatedly over a period of several weeks. Available evidence suggests that many flights terminate near their starting points and that in heavily infested fields a minority of the males call each evening. Pair formation and sexual competition in these species deserve further study. Most flights probably involve more than colonizing new or better fields or finding a willing source of conspecific sperm. T.G. Forrest (1983) has shown that calling males vary greatly in their attractiveness to females. On an evening when one calling male attracts no female, another, calling nearby, may attract more than 20! (He cannot service so many--Forrest prevented them from reaching the male.) Male attractiveness correlates with loudness of the calling song. Loudness correlates with both male size and soil moisture, which in turn are indicative of male quality and habitat quality. Scientists have exploited the attractiveness of loud calls by broadcasting simulated mole cricket sounds more than 30 times as powerful as the loudest male and have collected as many as 8000 mole crickets at a single sound source in a single evening.
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Scapteriscus is a genus of insects in the family Gryllotalpidae, the mole crickets. Members of the genus are called two-clawed mole crickets.[1] They are native to South America.[2] Some species have arrived in other regions (by flight or as contaminants of ship ballast or cargoes), including parts of North America, where some have become invasive and have become established as pests.[1]
These are medium-sized or large mole crickets characterized by the structures on their forelegs: two sharp claws and a blade-like process with a sharp flange or tooth. Other mole crickets have three or four claws.[3] Like other mole crickets, these burrow in the ground and the males produce calls with their tegmina.[4]
Scapteriscus species have been called "the most damaging crickets in the New World".[1] The major pest species include S. abbreviatus, S. borellii, S. didactylus, and S. vicinus.[5] These burrowing insects are pests of lawns, pastures, and gardens.[1] Some species feed on plant roots and seedlings,[6] while others are carnivorous and damage turf with their digging activity.[7] They are notorious in the Southeastern United States, where they have been called "the most damaging insect pests of turf and pasture grasses in Florida".[2] S. didactylus is invasive in Australia, where it damages turf, especially on golf courses, and attacks crops such as rice and peppers.[8]
In French Guiana, S. didactylus is a predator of the eggs of the critically endangered leatherback sea turtle (Dermochelys coriacea).[9]
Agents of biological pest control have proved effective for these mole crickets.[10] The nematode Steinernema scapterisci kills the mole cricket by carrying bacteria into its body, introducing an overwhelming infection.[1][11] The tachinid fly Ormia depleta is a parasitoid that leaves its carnivorous larva on the body of the mole cricket[12][13] The crabronid wasp Larra bicolor (family Crabronidae) catches the mole cricket and sticks an egg to it. When the larva emerges, it consumes the mole cricket alive.[14][1]
In 2003, 21 species were in the genus.[4] More have since been described.[3]
Two species of Scapteriscus were separated and placed in the new genus Indioscaptor.[4]
Scapteriscus is a genus of insects in the family Gryllotalpidae, the mole crickets. Members of the genus are called two-clawed mole crickets. They are native to South America. Some species have arrived in other regions (by flight or as contaminants of ship ballast or cargoes), including parts of North America, where some have become invasive and have become established as pests.
