Natural Histories And Biotic Associations

Development

In oviparous species such as European earwig, Forficula auricularia, and ringlegged earwig, Euborellia annulipes, clutches of ovoid, creamy white eggs are laid in protected burrows; eggs can be up to 2 mm in length in larger species. Nymphs generally resemble adults but can be distiguished from them by lighter color, shorter antennae, a male-type 10-segmented abdomen (rather than the 8-segmented abdomen of the adult female), and typically female-type forceps. Sexes are not easily distinguished externally in nymphs.

Habits

Most earwigs are thigmotactic and nocturnal, inhabiting crevices of various types, bark, fallen logs, and debris. Cavernicolous (cave-dwelling) blind species have been reported in the Hawaiian islands and in South Africa. Food typically consists of a wide array of living and dead plant and animal matter. Some earwigs have scent glands opening onto the dorsal side of the third and fourth abdominal segments, and from these they can squirt a foul-smelling yellowish-brown fluid some 10 or so cm, presumably for protection.

Reproductive Strategies

Among the Forficulina, reproductive strategies range from oviparous iteroparity (many clutches, the likely ancestral condition) to semelparity (one clutch, a trait derived in colder climates). In contrast, the Hemimeridae are viviparous ectoparasites, residing in the fur of central African rats of the genera Cricetomys and Beamys and dining on the skin and body secretions of the host, while the viviparous Arixenina are ectoparasites of bats.

Natural Enemies

Some beetles, toads, snakes, birds, and bats have been reported as predators of earwigs. F. auricularia can be parasitized by gregarines (sporozoans, which may be harmless) in the gut, as well as nematodes, cestodes, mites, and tachinid flies (a potential biocontrol agent). A fungal parasite has also been associated with several earwig species.

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