CropsLife cycle, population dynamics
- Les Coccidae
There are two to three larval stages in males and females. The larvae are mobile as well as the females prior to attachment, shell enlargement and hardening, and spawning (Figure 1).
- Parthenolecanium corni (Bouché, 1844), dogwood and vine lechanine
Univoltine species whose reproduction is sexual. Stage 2 larvae overwinter in the bark folds of the vine or on the twigs (September-April). In April, the fertilized female or not grows bigger and fills the forming shell with the eggs. The incubation of the eggs lasts 15 to 30 days. Each female lays 1,500 to 2,000 eggs.
The young first instar larvae colonize especially the underside of the leaves, they are placed near the veins to feed. The exuviae indicate the moult and the passage to the second larval instar. Before the leaves fall, the larvae migrate to the vine and the lignified twigs.
- Parthenolecanium persicae (Fabricius, 1776), peach shell
It is a probably bivoltine species, with parthenogenetic or bisexual reproduction. Each female lays 1,000 to 2,500 eggs. The larvae appear at the end of June. The young larval stages live on the underside of the leaves, the L2 stage appears in August, the L3 stage between September and October. It is the latter which overwinters on the twigs and the vine. The following spring, the imaginal moult gives birth to adult females.
- Pulvinaria vitis (Linnaeus, 1758), vine flake cochineal
Univoltine species in Europe with bisexual reproduction. We have the same migration phenomenon as in Parthenolecanium spp. The visacac adheres to the lower part of the abdomen and is made up of a ball of waxy threads where the eggs are deposited. The laying period lasts between late April and June, hatching takes place between late May and June.
The young larvae colonize the leaves. There are three stages with a first moult in July then a second in August. The adults appear in September, the mating season. These are the fertilized females which overwinter by colonizing the vine and the hardened twigs.
- Neopulvinaria innumerabilis (Rathvon, 1854), maple flake cochineal
This species is univoltine and it is the young fertilized female that overwinters on the vine. In May-June, the female remains glued to the winter support. Just before spawning, the abdomen is lifted and rejects long waxy filaments. The very numerous eggs (more than 8000) remain agglomerated until June then the larvae hatch. The L1 stage attaches to the leaves, the first moult takes place in July. Males appear in September giving rise to mating. The fertilized females migrate to the woody parts.
- Pseudococcidae , or mealybugs (mealybugs)
In this family all the stages are mobile. Females (except H. bohemicus because ovoviparous) build a large ovisac in which the eggs are laid. Males have a lifespan of one to a few days and die after mating.
- Heliococcus bohemicus Šulc, 1912, Bohemian scale
This species is univoltine. The insect overwinters under the bark of the vine, at stage L2. In April there is migration towards the young leaves. After mating, the fertilized females return under the bark to lay eggs and stop feeding.
The neonate larvae are expelled alive from the females (ovo-viviparity). The laying period takes place between early June and mid-August. The L1 larvae colonize the leaves, molt during the summer and at the L2 stage migrate under the bark before the leaves drop in October.
- Phenacoccus aceris (Signoret, 1875), apple or plane tree scale
This species is univoltine. These are the L2 larvae that overwinter in crevices under the bark. In the spring, they give birth to males and females. Mating takes place in May and females lay eggs in June. These can be housed in ant nests. Females lay 800 to over 3000 eggs. They die after spawning.
The eggs hatch after a month of incubation and the L1 larvae colonize the leaves and then molt during the summer. The L1s are very mobile, while the L2s will simply migrate to the woody parts in October.