Top 20 Most Common Insects in Ljubljana

The old World swallowtail (Papilio machaon) is commonly just called the "swallowtail," giving it the added title of "old world" to distinguish it and remind us that it comes from the "old world" (Asia, Africa, Europe). The upper side of them is a beautiful combination of pure white with black striping, the underside being a brownish version of the same thing. There is blue and two red dots on its back side.

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.

Ochlodes sylvanus has a wingspan of 28–32 mm, which is similar in size to Chequered skipper. Although called "large" this is still a relatively small butterfly and not much larger than either the small or Essex skippers. The body is rather squat. The antennae are hooked at their tips. The upperside of the wings is orange-brown with a brown border and some lighter spots. The underside of the hindwings is greenish-yellow, marked with sparse yellow spots. The male has a broad scented androconial dark line across the top of the forewings. On the hindwings of the females there are brighter square marks. When the wings are opened, the forewings are obliquely folded, masking the hindwings. The faint chequered pattern on both the upperside and underside, and also the hook-shaped antenna tips, help to distinguish the large skipper from these two orange skippers. The Lulworth skipper also has patterned wings, but does not have the hooked antennae. The caterpillar can reach a length of 28 millimetres (1.1 in). It has a large blackish-brown head and a bluish green body, with a dark line down its back and a yellow stripe along each side.

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.

Western honey bee（Apis mellifera） is the most common species of honeybee in the world. Among the first domesticated insects, its cultural and economic impact on humanity has been vast and far-reaching, providing honey, wax and its services as a pollinator. Western honey bee faces challenges worldwide, such as colony collapse disorder, and populations are thought to be decreasing.

The jersey Tiger is often spotted flying above flowers in gardens and meadows from mid-summer to early fall. The moth’s patterned wings act as camouflage, making the insect difficult to spot when resting on foliage. The caterpillars feed on nettle, ground ivy, and other types of plants, making them an occasional pest in some gardens.

The great green bush cricket (Tettigonia viridissima) is found in any type of open land, including grasslands, parks, and edges of woodlands. It prefers warm, dry habitats, where it lays its eggs overwinter. It primarily feasts on smaller insects, but it also eats some plants too.

The white-legged damselfly or blue featherleg (Platycnemis pennipes) is a damselfly of slow-flowing, muddy waters. It occurs from the Atlantic to Siberia and is often abundant throughout its range.

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.