Top 20 Most Common Insects in Bilbao

The speckled wood (Pararge aegeria) prefers to live in damp, dark woodlands. Unlike other butterflies, it's more active in shadier habitats rather than sunny ones. Males often fight over a perch, spiraling up to the treetops until they determine a winner. These perches are where the males find passing females.

The meadow brown (Maniola jurtina) is similar to the Gatekeeper in the way that it rests with its wings open due to the "eye spots" on either end of its wings that ward off predators. While the color is a deep brown, the caterpillar form is a beautiful bright green with little, white hairs and a dark line leading down its back.

The asian hornet (Vespa velutina) is a predatory species, preying primarily on deceased animals and arthropods, including honey bees. Because of this, it's a major pest for the beekeeping industry, weakening and destroying honey bee hives. The females have a stinger that can inflict pain on humans, but the males do not.

Red admiral (Vanessa atalanta) is a visually striking species of butterfly. Unusually territorial, males will compete for choice areas, and females will only mate with males that maintain their own territories. This butterfly is known for being particularly patient with human interactions, even to the point of perching on clothing or flesh.

Colias croceus has a wingspan of 46–54 millimetres (1.8–2.1 in). The upperside of the wings is golden to orange yellow with a broad black margin on all four wings and a black spot near the centre forewing. Usually these butterflies settles with its wings closed, consequently the black margin of the uppersides of the wings is difficultly visible. The underside lacks the black borders and is lighter, with a more greenish tint, particularly on the forewings. In the forewing underside is the same dark spot as on the upperside, but often with a light centre; the hindwing underside has a white centre spot, often with a smaller white or dark dot immediately above it. Sometimes, a row of black dots occurs on the underwings' outer margins, corresponding to where the black border ends on the upperside. Females differ from the males in having yellow spots along the black borders on the upperside. In flight, Colias croceus is easily identifiable by the intense yellow colouring, much brighter than that of the lemon-yellow male common brimstone which also lacks black markings. Like all Colias species they never open their wings at rest. In a small proportion of females (about 5%) the golden upperside colouration is replaced by a pale cream colour. These females have been distinguished as form helice. The pale form helice does not seem to be that distinct as intermediates exist and the variation is to some extent related to humidity during development, with dryer conditions producing paler colouration. These pale forms helice can be confused with Berger's clouded yellow (Colias alfacariensis) and the rarer Pale clouded yellow (Colias hyale). Even the palest C. croceus tends to have more black on the upperside however, in particular on the hindwings. Young caterpillars are yellow-green, with a black head. Later they become completely dark green, with a white red spotted lateral line after the third moult. The pupae are green and have a yellow side stripe. This species is rather similar to Colias myrmidone, Colias chrysotheme, Colias erate, Colias hyale, Colias alfacariensis, Colias caucasica, Colias aurorina.

Common brimstone (Gonepteryx rhamni) is an attractive species of butterfly; males display iridescence and have yellow wings, whereas females have white-green, non-iridescent wings. This species is wholly reliant on two species of buckthorn plant to lay its eggs. Consequently, the larvae consume large amounts of buckthorn.

European peacock (Aglais io) is a colorful butterfly that resides in temperate Asia and Europe – hence its common name. Its prominent eyespots deter would-be predators, who mistake them for the eyes of a bigger, more dangerous species. In recent years, this species appears to be expanding its range into previously uncolonized territory.

It rests with closed wings when not in flight.

Despite its common name, only male specimens of common blue butterfly (Polyommatus icarus) can accurately be described as blue; the females are predominately gray-brown, with only a dusting of blue and a scattering of orange spots. The adults live for only three weeks before dying.

The greater stag beetle ( Lucanus cervus ) is popular with insect lovers. The male individual is known for the impressive jaws that look like antlers of a deer. In contrast, females do not have jaws and are much smaller. The adults feed on juices and tree saps while the larvae eat wood. By the way, greater stag beetles are considered a pest in the Middle East where they dig into the root systems of date palms, affecting the date crop.