Summary
Gryllus bimaculatus is a species of cricket in the subfamily Gryllinae. Most commonly known as the two-spotted cricket, it has also been called the "African" or "Mediterranean field cricket", although its recorded distribution also includes much of Asia, including Korea, China and Indochina through to Borneo. It can be discriminated from other Gryllus species by the two dot-like marks on the base of its wings. The species is popular for use as a food source for insectivorous animals like spiders and reptiles kept as pets or in zoos. They are easy to raise and do not require prolonged exposure to cold in order to complete their life cycle.
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Behavior
Fighting In the wild, male crickets do not tolerate one another and will fight until there is a winner. The loser usually retreats without serious injury. The fighting method involves opening the mandibles as wide as possible, gripping the opponent's mandibles and pushing with the hind legs. Chirping Male crickets of this species produce several distinctive chirps, though each sound is made by rubbing the two outer wings together. Loud and steady chirps made throughout the night are to attract females and to warn off other males. Loud fast-frequency chirps are emitted when males encounter one another and are preparing to fight. They are intended to frighten off the rival male. There are two other chirp patterns that can be observed in their mating behaviors. A soft clipping sound, 'calling' song, is made when a female is known to be nearby but in a certain distance, and more rigorous sound, 'courtship' song, is made when a female is close enough to mate (mounting on the male's back). These two song can be easily distinguished by human ear based on its chirp patterns and frequency components. Song pattern and body size Whether cricket song pattern (e.g. frequency spectrum) reflect song-emitter's body size is controversial. A recent study failed to detect body-size effect on both calling and courtship songs of G. bimaculatus. Shelter These crickets hide under logs, in grasses, and in crevices. They also dig holes in the ground to create homes, or live in holes created by other animals. Males are territorial and will fight off other males, but allow any number of females to coexist in the same shelter. Cannibalism Cannibalism is extremely rare, but females have been observed to eat males if there is not enough food to eat. Circadian rhythm Pigment Dispersing Factor has been implicated in the nocturnal rhythms of crickets.
Breeding
Females have a tubular organ at the rear, known as an ovipositor, which is used to lay eggs into the ground. They lay their eggs into humid soil and the baby crickets hatch in about two weeks. Polygamy Gryllus bimaculatus exhibit polygamy, in which one individual has many different mates. Variation of polygamous behavior occurs between males and females, within a population of Gryllus bimaculatus. Both females and males continuously seek mates with whom they can spread their seed. Polyandry is the most common form of polygamy practiced in G. bimaculatus. This means that female crickets will mate with more than one male. Male crickets do not exhibit polygyny.
Economic importance
Gryllus bimaculatus is widely used by suppliers of live crickets for feeding to pet and zoo animals.
Genome
The first version of the Gryllus bimaculatus genome assembly and annotations was released in 2020 and published in the journal Communications Biology in 2021. This genome has a length of 1.66-Gb and contains 17,871 annotated protein coding genes.