Vibidia duodecimguttata can reach a length of about 4 millimetres (0.16in).[3] These beetles have an oval shaped body. The light brown antennae are quite long. The elytra have a slightly wider side edge. Their entire body has a light brown basic color on the upper and lower side, only the eyes are black. Elytra show 12 whitish spots, six on each elytron (hence the Latin word duodecimguttata, meaning twelve-spotted as if by drops). There is a whitish spot on both sides of the throat.
Adults can be encountered from April through September. This beetle is mycophagous,[4] mainly feeding on the powdery mildew fungus (Oidium), diseases affecting some trees (including oak and hazel).
Mating behavior
First, the chase is expressed in rapid movements, with the male pausing for a moment at least twice before courtship.
Courtship consists of the male mounting the female's elytra and lapping her, turning twice with the aedeagus extended
After that, the mounting is approx. 1 second.
During mating, the male, in addition to making body turns, as in Psyllobora vigintiduopunctata, unlike it, the males of this species also make a head protrusion forward and down after the completion of each turn.
Vibidia duodecimguttata, copulation
Eggs and oviposition
The egg laying begins about 1 week after mating. The eggs are similar to those of the 22-spot ladybird, but the green hue on the outer shell is slightly more intense and their tip is more pointed.
Eggs of 12-spot ladybird
The eggs are laid in an individual clusters.
Larval stages
Hatchlings
The main color of the newly hatched larva is transparent grey. The four spots on the first two segments after the pronotum are much larger, compared to the remaining tubercules on the remaining segments. The spots are dark grey, while the abdomen is more elongated even in this instar. The legs are grey exactly like the color of the body. The tubercular hairs are dark. The head is much darker grey with a light area only in one place between the eyes. The length is 3.1 mm.
The hatched larva is very opportunistic and moves quickly in exploring the leaf surfaces. The time from hatchling to the 1st instar is 24 hours.
Newly-hatched larva of Vibidia duodecimguttata
First instar
In the 1st instar the larva elongates a little and turns slightly yellow. The legs become dark gray, and the pronotum fades. The head is darkened and is almost black. The duration of the first stage is 2,8 days.
1st instar larva
Second instar
In the second instar, the body reaches 4,5 mm in length and acquires a brighter yellow color. On the two segments after the pronotum above the pairs of spots, there is a yellowish shade. The pairs of black spots are limited in size to some hemispherical oval ones. The pronotum is slightly faded. On the forehead between the eyes with a single dark spot. The head becomes lighter in dark yellow-pale gray color. The legs are paler and transparent.
2nd instar larva
Third instar
The larvae reach the 3rd stage, after 3 days spent in the 2nd. The larva. The early 3rd stage is 4 mm long, while the late one is 7 mm.
The body now acquires an overall electric green hue, without the abdominal side, and the two yellow stripes are still in the form of dots on each abdominal segment. In the middle of the pronotum and on the other two segments after it there are 4 light squares next to each other.
3rd instar larva (take a look at the pale yellow color)
Fourth instar
The 4th instar larva is light yellow-beige with a very faint orange tint, which is less than 1% of its color. The legs are the same color as the body. On the dorsal side of the abdomen on the side there are two pale yellow lines, along with three rows of black spots. The two segments after the pronotum with two pairs of black spots and a few vague shadows. The pronotum is mostly electric yellow and only below there are beige spots.
Vibidia duodecimguttata larva in the 4th (last) instar
Head dark beige. Fully grown, the larva is about 17 mm long. The fourth instar in this species is very short, compared to others, lasting only 3 days, and then the larva enters a prepupal state under the fungus-infected leaves of trees and tall shrubs.
Larva, pronotum detailsLarva, ventral
Pupa
It is pale and creamy yellow in color, and on both sides along the length of the sternites from the 4th to the end there are a number of yellow spots (which are also electric), until they do not completely cover the last 6th sternite and only a small gap remains. This species forms its pupae only under the leaves infected with fungi.
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