Dermaptera (Earwigs)

Overview :

Current information regarding Earwig population occurrences in the Valle Della Luna is primarily taken from first-hand observation during Spring (Pre-Vernal/Vernal) 2018 and largely by literature review. The scientific paper 'I Dermatteri Di Sardegna' (Taglianti, 2011) has been tremendously useful in providing data indicating Dermaptera species present in Sardinia, more specifically the Olbia-Tempio and Sassari regions local to Capo Testa and differing habitat types. There are 45 species occurring in Europe (most are Forficulina), with 25 species present in Italy and 9 species inhabiting Sardinia. According to criteria set out in 'I Dermatteri Di Sardegna' 8 species are of possible occurrence, some more likely than others. The species identified for further research are set out as follows (click on species name below for profile), although very little is known about the behaviour, habits and Cenosis (interactions within specific ecosystems) of many species. The common European Earwig (Forficula auricularia) on the other-hand is well documented, so in-depth information about its nature, reproduction, lifespan, behaviour, communication/perception, food habits and predation can be provided, and to a point can be inferred to other species.

Observation of large numbers of Earwigs in Spring 2018 indicate the likelihood of common occurrence, with specialist habitats, for instance: Rocky/Sandy Shores & Macchia requiring further in-depth study by direct searching, using pitfall traps, beat-sheet and sifting research techniques .

Forficula decipiens - Olbia Tempio, Sassari - Very Likely.
Forficula auricularia - Olbia-Tempio, Sassari - Likely.
Forficula pubescens - Olbia-Tempio, Sassari - Possible.
Anisolabis maritima - Olbia-Tempio - Possible.
Labidura riparia - Olbia-Tempio, Sassari - Possible.
Euborellia moesta - Olbia-Tempio, Sassari - Possible.
Nava lividipes - Olbia-Tempio, Sassari - Possible.
Labia minor - Sassari - Less Likely.

forficula famiglia.JPG_2013126153022_for

Forficula decipiens (Isperragoa)

000001 fnm 05-03-2017 Litoranea Alghero-

Above left: Female with young, Above right: Male, note larger & curved pincers.

Identification: 15-19mm. Head: yellowish-orange. Abdomen: reddish-brown. Pronatum, tegmina & legs: Yellowish. In both sexes. Similar to Forficula aricularia (Common European Earwig) differing in colouration, known to exist in symbiosis in some sites (Taglianti 2011).

Habitat Preferences: Characteristic of Thermophilous-Mediterranean bioclimate, in open-formations such as under rocks and dry-meadows (Servizip PID, 2007), but also in Ecotones of Forest, Macchia & Garriga (Taglianti, 2011). Especially bushy habitats close to the sea (Muranyi, 2013). Particularly common in central & southern Tyrrhennian regions in Sardinia, Corsica & Sicily. Widespread in smaller islands, is often the only species of Dermatory (Earwig) present (Taglianti, 2011).

Habitat Interactions: "Very common year round under rocks and under the bark of trees" (Gene,1837). During the day they prefer dark, moist places to hide from predators. During mating season females prefer soil sites, in which to burrow, hibernate & deposit eggs, approx. 5-8mm in depth (University of Michigan ADW - Forficula auricularia, 2014).

Trophic Level (Food-Web): Level 2/3 as Scavengers & Predators.

Ecosystem Interactions (Biocenosis): Omnivorous but mainly Phytophagous on living & decaying Plants, Lichens & Algae. On other organisms both dead & alive, including Aphids, Mites, Maggots, Spiders & Protozoans. In other words they do not seem to be particularly picky eaters. They are preyed upon by Tachinid-Flies, Birds, Reptiles & a range of Beetles (especially Ground-Beetles) (Inferred from 'University of Michigan ADW - Forficula auricularia, 2014 & Primary Observations).

Significance (in Valle Della Luna): Important Mid-Trophic species as a component of localised food chains, providing a large timely food resource for predator species early in the year, before Birds, Reptiles & Beetles emerge in abundance. Conservation status unknown (non-regulated species).

Further Research: To be conducted in Pre-Vernal, Vernal, Aestival, Autumnal & Hibernal parts of the Ecological Calendar - by Direct Searching, Dry-Pitfall Traps & Beat-Sheets.

Identification of populations and Biomass-hypothesis.
Exact habitat preferences.
Ecosystem Interactions: Preferred food plants, specific prey & predator species.
Substrate (Soil) preference for nesting/hibernation.
Behavioural monitoring where possible.

Behavioural Notes: Found commonly in Spring on plant specimens (flowers & foliage) in Arborescent Matorral/Garriga/Macchia close to the sea, whose populations support large communities of Aphids. Please refer to the 'Forficula auricularia' profile for inferred data relevant to the below listed elements. This information is currently unknown but as the species are very similar, behaviours may well be very similar also:

Behaviours Description.
Reproduction.
Lifespan.
Communication & Perception.

Forficula decipiens

Above left: Habitat-type, Above right: Male Labidura riparia threatened by predator.

Labidura riparia (Striped Earwig)

Habitat Preferences: Coastal/Riparian, along margins of various water-bodies, a preference for sandy underground habitats from beaches to riverbeds (Foottit & Addler, 2018). From tropical to sub-temperate regions. Characteristic of Sandy-coast communities (Psammophilous), particularly the stretch at the front of dune formations. Shoreline to Fixed-Dune habitats (Taglianti, 2011).

Habitat Interactions: Found in a variety of niches, although generally sand dwelling, the primary environmental characteristics being dark, sheltered & moist to hide from predators in the day-time. For instance, moist-sand underneath vegetation. L. riparia tends to penetrate deeper into the soil than most species of other Earwigs. Special nests are dug for molting, feeding & egg-laying, usually under a rock (or tree bark) by the female. They loosten the sand with their forelegs & transport it in their mandibles, thus excavating burrows approx. 10-40cm deep, in which they rest in the day. Their burrow also acts as a winter quarter from which they re-emerge the following year (vernal/aestival). In the summer (aestival/serotinal) they excavate a brood chamber in the soil, where the female deposits her eggs and remains with them for the 9 day embryonic period. Food is stored in the burrow (Gunther & Hernez, 1974. Harz, 1957,1960).

Trophic Level (Food-Web): Level 2-4. Primarily as a generalist Predator, also as a Scavenger.

Ecosystem Interactions (Biocenosis): Omnivorous but with a dietary preference for animal nutrition. They have a preference for Lepidoptera larvae & insect eggs, but will eat any available insec. In the littoral zone they prey upon small crabs, beetles, flies & other insects. In drier locations they hunt millipedes, spiders & hairless caterpillars (Eisenbeis & Wichard, 2012). Because of their flexible eating habits they adapt well, as long as their are insects around. In abscence of a ready food supply, they have been known to eat nymphs/eggs of their own species. They eat primarily just after sunset (Tarwik, 1973). Their primary predator is ants, as they

feed on unattended eggs. Overlap of predation does occur between organisms though, as Striped Earwigs prey on Ant eggs. The effect of the Ants on the Earwig populations has been found to be greater than vice-versa (Gross, 1969). Other predators include a range of animals; Carabid & other Beetles, Grasshoppers/Crickets, Spiders, Centipedes, Lizards, Birds & other Insectivores (Eisenbeis & Wichard, 2012.

Significance (in Valle Della Luna): Unknown to be verified as present. In Sardinia the Shoreline-Fixed Dune system is becoming rarer due to anthropogenic actions, i.e. seaside tourism. this ideal habitat for Striped Earwigs has been categorised as under rapid reduction and disappearance (Taglianti, 2011).

Further Research: To be conducted in Vernal, Aestival & Autumnal parts of the Ecological Calendar - by Direct Searching & Dry-Pitfall Traps.

Identification of populations.
Exact habitat preferences.
Behavioural monitoring where possible.

Behaviours Description.
Reproduction.
Lifespan.
Communication & Perception

valle della luna ecology