Steinernema scapterisci

Mole cricket nematode
Scientific classification
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Secernentea
Order:	Rhabditida
Family:	Steinernematidae
Genus:	Steinernema
Species:	S. scapterisci
Binomial name
Steinernema scapterisci Nguyen & Smart, 1990

Steinernema scapterisci, the mole cricket nematode, is a species of nematode in the order Rhabditida. It is a parasite of insects in the order Orthoptera, the grasshoppers, crickets and their allies. It has been introduced into Florida in the United States in an effort to provide a biological pest control of mole crickets.

Steinernema scapterisci can be distinguished from other species of its genus "by the presence of prominent cheilorhabdions, an elliptically shaped structure associated with the excretory duct, and a double-flapped epitygma in the first-generation female." It does not hybridise with Steinernema carpocapsae, and it infects and kills fewer than 10% of the non-orthopteran insects with which it comes in contact. Larvae of the wax moth, which all other known species of Steinernema infect, are not parasitised by this nematode.

S. scapterisci is native to South America, with its range including Argentina, Brazil and Uruguay. It is more tolerant of high temperatures and less tolerant of low temperatures than are other members of its genus.

Individual adults of S. scapterisci are either male or female and their entire life cycle takes place within the host insect. This comprises an egg stage, four larval stages, the third of which is infective, and an adult stage. Depending on the conditions and the abundance of the parasite, there is either a short life cycle or a long one. The short cycle lasts six to seven days and occurs when the population of nematodes is dense and the availability of nutrients low. In this, the eggs develop through the four larval stages to first generation adults. These mate and the developing larvae become infective in the third juvenile stage. When nutrient availability is high and the nematodes are not overcrowded, the long cycle kicks in. This at first follows a similar course to the short cycle, but the eggs from the first generation adults develop through four larval stages to second generation adults. It is the eggs from these that develop into infectious juveniles. This cycle takes about ten days.

The infectious juveniles can survive in the soil for eight weeks or more. They infect any mole cricket that passes, entering its body through its mouth or spiracles and moving into the hemocoel (body cavity) which is filled with hemolymph. Here they liberate a specialist bacterium, Xenorhabdus innexi; this causes sepsis in the host insect, eventually killing it, but not before the nematode has passed through its various life cycle stages and further infective juveniles have developed. Some fifty thousand infective juveniles may have been released into the soil by each mole cricket host by the time it dies.

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Wikipedia