Top 20 Most Common Insects in Azores

The japanese Beetle (Popillia japonica) was introduced to the Americas from a tourist's car in Nova Scotia. This beetle has been limited in its ability to fully infest the environment, but cannot be fully eradicated. A swarm of them have been known to strip an entire peach tree in a matter of minutes.

Mythimna unipuncta, the true armyworm moth, white-speck moth, common armyworm or rice armyworm, is a nocturnal agricultural pest belonging to the family Noctuidae. This moth is also commonly referred to by the scientific name Pseudaletia unipuncta. The species was first described by Adrian Hardy Haworth in 1809. Mythimna unipuncta is found in the Americas and in parts of Europe, Africa and Asia. Its original distribution is North and South America. It has been introduced to other places from there. They are known as armyworms because the caterpillars move in lines as a massive group, like an army, from field to field, damaging crops. The true armyworm has a distinct migration pattern in which they travel north in the spring and south in the fall to ensure that mating occurs in a favorable environment in the summer. While progressing through the life cycle stages of egg, larva, pupa, and adult, this species must avoid attack from predatory bugs, birds, wasp and fly parasitoids, and bacterial and fungal diseases. As polygamous insects, females release sex pheromones and choose multiple males as mates. The production and release of the pheromones are influenced by temperature, photoperiod, and the juvenile hormone. Hearing is an important sense for the true armyworm, necessary for mating and evading bat predation.

The portuguese millipede (Ommatoiulus moreleti) is an herbivorous Myriapoda, meaning "many-legged". It feeds on decaying wood, fungus, and leaf litter, so it can be considered a pest in large quantities. While it cannot harm humans, it can invade homes and destroy crops.

Large white (Pieris brassicae) is visually similar but quite larger than its close relative P. rapae. It lays its eggs on food plants such as cabbages – the origin of its common name – leading to many farmers' classifying this species as a pest.

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.

Generally a very common species, the strawberry Seed Beetle is a ground beetle that feeds on a wide array of seeds and insects. Adult beetles are considered a serious pest of grain cereals and other plants such as strawberries. It is a nocturnal insect that sometimes enters houses, following the source of light. It has wings, but it rarely seems to fly.

Tenuiphantes tenuis is a species of spider belonging to the family Linyphiidae. Its native distribution is reported as Europe, Macaronesia, Northern Africa, Turkey, Caucasus, Central Asia. The species was introduced to USA, Chile, Argentina and New Zealand from Europe where it is found throughout. The body length excluding legs is about 2 to 3 millimetres (0.079 to 0.118 in). The carapace is dark brown. The abdomen often has a distinctive pattern, usually with clear black spots, and T. tenuis is more slender than other species in the family. The legs are brown and lack annulations. T. tenuis is usually found in low vegetation, moss, and leaf litter where it feeds on various insects including Listronotus bonariensis.

The spirea aphid is a major pest of agricultural crops, including citrus, apple trees, brassicas (such as cabbage and broccoli), and plants in the Spiraea genus. They can feed on many different species and most often eat the buds, flowers, and leaves of the host plants.

European earwig (Forficula auricularia), despite its name, is a common household occupant across North America. This species distinct differences in appearance between sexes, with males possessing obviously curved pincers whereas those of females are relatively straight. It is a noted agricultural pest and may exude an unpleasant odor, clustering near human dwellings.

An interesting subject of folklore and myths, the devil's Coach Horse Beetle has long been associated with the Devil and sinister forces, hence its common name. This fast-moving beetle is a voracious predator of other insects and invertebrates. Although it has the ability to fly, it rarely does.