Dermaptera: Labiduridae: Labidura riparia (Pallas, 1773)
(written by Jessica Houle)
Labidura riparia (Pallas, 1773) is a species of earwig (Order: Dermaptera, Family: Labiduridae), first described by Peter Simon Pallas as Forficula riparia 1. Its common names are the giant earwig, striped earwig, or tawny earwig, and it can be found throughout Europe and the southeastern US: Florida, Arizona, California, and Texas. It is an introduced species in the US that lives in debris near aquatic environments like ponds, streams, and shorelines, as well as in agricultural fields (2, 3). It is light brown in color and if disturbed, it can release a strong odor which nauseates most people (3).
Morphology:
Like other earwigs, L. riparia undergoes gradual metamorphosis. The adult earwigs have highly reduced fore wings called tegmina that cover folded hind wings (4). They also have forceps-like cerci on the abdomen which can be used by males to fight each other or attract females, as well as serve as defense weapons (5).
Mating/Parental care:
It is typical to see parental care in Dermaptera. After spending winter together in the soil, the male and female build a brood chamber. Once the female has mated and laid her eggs, she usually kicks the male out of the nest. She then protects the eggs from predation, desiccation, and mold by watching over, turning, and cleaning them. As seen in several other species of earwigs, the mothers of L. riparia stay with the nymphs through several instars, providing food to the offspring (4).
Diet:
Dermapterans are considered omnivores and can also be found feeding on decaying matter (4). Most diet studies using L. riparia focus on their predatory habits. Due to their abundance in agricultural fields, they are studied for their potential as a biological control of major pests, including noctuids, aphids, coleopteran larvae, and cabbage loopers (2,7). In one study, L. riparia were shown to become abundant and effective predators in a field containing residues of cyclodine chlorinated hydrocarbon pesticide, which killed off other major predators like ants (8).
Evolutionary Significance:
L. riparia represents an interesting case in evolution. This species falls into one of a few families of Dermaptera where the male has two penises. Dual penises are not unique to only Dermaptera and can be found in fairy shrimp, dragonflies and spiders. However, what is intriguing is the evolution of a preference for the right penis, which is kept in ready position by 90% of the population. Individuals without this preference or those with right-ablated penises are equally successful in mating. More derived species like Spongiphoridae, Forficulidae and Chelisochidae only have one penis, suggesting that the ancestor of all Dermapterans had two (9).
NC State Collection:
The museum contains no less than 135 specimens for L. riparia, with a majority from North Carolina but also specimens from Honduras, Florida, Texas, Arizona, Louisiana, and Georgia.
Find out more:
1. BugGuide. Labidura riparia.
2. Wadoill, VH (1978). Sexual differences in foraging on corn of adult Labidura riparia [Derm.: Labiduridae]. Entomophaga 23: 339-342.
3. Choate, PM. (modified from Hoffman, 1987) The Order Dermaptera (Earwigs) in Florida and the United States.
4. Ramel, G.
5. van Lieshout, E., M. A. Elgar. 2009. Armament under direct sexual selection does not exhibit positive allometry in an earwig. Behav. Ecol. 20(2): 258-264.
6. Shepard, M.,Waddill, V., Kloft, W. (1973). Biology of the Predaceous Earwig Labidura riparia (Dermaptera: Labiduridae). Annals of the Entomological Society of America 66(4): 837-841.
7. Strandenberg, JO (1981). Activity and Abundance of the Earwig, Labidura riparia, in a Winter Cabbage Production Ecosystem. Environmental Entomology 10(5): 701-704.
8. Tryon, E.H. (1986) The Striped Earwig, and Ant Predators of Sugarcane Rootstock Borer, in Florida Citrus. The Florida Entomologist. 69(2): 336-343.
9. Palmer, A.R. (2006) Caught Right-Handed. Nature 444:689-691.
