Labidura riparia, Striped Earwig; (Dermaptera: Labiduridae)

Sarah McComic, Huval, Forest, Carlton, Christopher E.

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Description

Labidura riparia, or the striped earwig, can be found throughout the world where appropriate habitats occur, especially in tropical to subtropical climates. It is considered beneficial in agricultural and garden setting because of its predatory feeding habits that include preying on common agricultural pests.

The striped earwig is one of the largest members of the order Dermaptera occurring in North America, with a body length of 3/4 of an inch to 1 1/4 inch (20 to 30 mm). The body is normally tan to light brown in color with some darker brown on the upper surfaces (dorsal). The darker markings form two stripes that run the length of upper surface of the thorax and forewings. Striped earwigs possess large brown compound eyes. The head is mainly dark brown in contrast to the tan body. Legs and antennae are light tan in color, similar to the body. The forewings are modified into leathery pads (tegmina) and the hind wings are folded beneath them in a complex, accordion-like pattern. The hind wings are only extended during flight. As with other earwigs, a pair of large forceps-like cerci extend from the tip of the abdomen. These are used in defense and as a prey-catching mechanism. The cerci are approximately one-fourth the length of the body, tan in color, tapering to darker brown tips. Males have longer and more curved cerci than females. Striped earwig nymphs are similar in overall shape to adults, except they are smaller, lighter in color, and the wings and cerci are less developed. Adult females lay light colored eggs that are 1/25 to 1/12 of an inch long (1 to 2 mm).

Striped earwigs are common in human-modified habitats and are known under other common names, including shore earwig, giant earwig and riparian earwig. A number of other species are similar, but the large size and striped pattern usually allows easy recognition.

Life Cycle

Adult female striped earwigs prepare a nest and lay 30 to 50 eggs in masses under debris and other protected, humid locations on the ground. Females care for and guard the eggs, frequently cleaning and rotating them, until the nymphs hatch. If the nesting site is disturbed, the female usually transports the eggs to a new, safer location. During the nesting period the female broods continuously over her eggs. After hatching, nymphs continue to be protected by the female until they are old enough to fend for themselves. During this stage of parental care, the female forages for food and returns to the nest to feed the nymphs a variety of insects and plant matter. Nymphs disperse and grow for about three months until they become adults. Each nymph passes through six growth stages (instars). Adult striped earwigs are mainly predaceous, feeding on a multitude of insects. Prey in agricultural systems include larvae of tobacco cutworm (Spodoptera litura), fall armyworm (Spodoptera frugiperda), cotton leafworm (Spodoptera littoralis), and the velvet bean caterpillar (Anticarsia gemmatalis). Once adult females have accumulated sufficient nutrition for egg development, they mate, typically during spring, and lay eggs a short time later.

Ecological Significance

Striped earwigs are distributed worldwide, but are more common in tropical and subtropical regions and in moist habitats. They are considered important natural control agents in agricultural systems and home gardens because of their predatory feeding habits, especially moth larvae of many important crop pests. They feed on eggs, larvae and pupae at night when they are most active, mostly on the ground, but occasionally on foliage above ground. Research has demonstrated that adult striped earwigs can rid cotton plants of up to 45% of moth pupae over a three-day period. In Louisiana, striped earwigs are common and constitute an important component of the natural enemy complex in many crops. Striped earwigs may be active most of the year in Louisiana but slow down during winter months and seek shelter in moist areas, often near bodies of water or wet field margins. An interesting defensive mechanism used by striped earwigs to avoid predation by small vertebrates is production of a foul-smelling secretion that mimics rotting flesh.

Striped earwigs can deliver a minor defensive pinch if handled, but are not venomous and pose no threat to humans or pets. Various species of earwigs may enter homes on occasion, but these are accidents and the insects cannot survive indoors. And old myth states that earwigs will burrow into a person’s ear and lay eggs. The name “earwig” comes from this belief. The origin of this myth is unclear, and it is completely false.

Control

Monitoring and surveillance. Striped earwigs do not warrant control in agricultural settings and home gardens. But some other earwig species are herbivorous and may cause damage to plants, especially to seedlings and other tender plant tissue. Correct identification is critical to correctly assess whether control is needed or not. Eliminating striped earwigs will increase damage inflicted by pest insects. If in doubt about the identity of earwigs found during crop pest monitoring, consult an entomology diagnostician for an authoritative identification and risk assessment.

Cultural control. All earwig life stages can be removed from inside homes by hand or vacuuming. They have the capacity to pinch, but they are incapable of inflicting damage. Caulk or weather stripping can be used to fill cracks to prevent earwigs from entering under doorways or around widows. Lastly, reduction or removal of moist debris (piles of leaves or mulch) where earwigs thrive will greatly reduce numbers.

Chemical control. No chemical control is recommended for striped earwigs. Damaging infestations of herbivorous earwig species can be eliminated with insecticides but this may result in only temporary control. Insecticide dusts sprayed into indoor cracks can reduce the number of earwigs and other insects that homes. Herbivorous earwigs in home gardens can be controlled by insecticide sprays or granules applied to the soil or mulch following correct identification. Make sure to always follow label instructions.

References

Byers J. A. 2015. Earwigs (Labidura riparia) mimic rotting-flesh odor to deceive vertebrate predators. Naturwissenschaften. Aug;102(7-8):38. doi: 10.1007/s00114-015-1288-1. Epub 2015 Jun 13. PMID: 26071006 (Accessed 7 March 2022).

Flint, M.L. Earwigs. 2012 ed. Pests in Gardens and Plants: University of California Agriculture and Natural Resources, IPM (Accessed 7 March 2022).

Hagen K. S., N. J. Mills, G. Gordh, and J. A. Mcmurtry. 1999. CHAPTER 16 - Terrestrial Arthropod Predators of Insect and Mite Pests, Editors: Thomas S. Bellows, T.W. Fisher, Handbook of Biological Control, Academic Press, Pages 383-503.

Langston, R. L., and J. A. Powell. 1975. The earwigs of California. Bulletin of the California Insect Survey 20. 30 pp.

Zungoli, P. A., E. P. Benson, and M. Ridgeway. Earwigs. 2003 ed. Home and Garden Information Center: Clemson University Cooperative Extension (Accessed 7 March 2022).


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Adult striped earwig in moist woody debris (@naturalistmars, iNaturalist.org, Creative Commons BY-NC 4.0).

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Eggs of striped earwigs in brood nest (Mandy Howe, www.spiders.us., Creative Commons BY-NC 4.0).

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Recently hatched striped earwig nymph (Mandy Howe, www.spiders.us., Creative Commons BY-NC 4.0).

2/16/2024 3:36:17 PM
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