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Photos of larvae in a massive attack on bird cherry trees

[Photo 1.]
© Photo Conny Andersson 2006


Welcome to this website! My name is Conny Andersson. I reside in the countryside of Sweden, in a place named Långö that is situated circa 90 kilometers north-east of Gothenburg (i.e. Göteborg in Swedish).

June 12, 2006

At noon on June 12, 2006, I was out walking. Suddenly, I saw something I never seen before in my lifetime. A group of naked bird cherry trees — Prunus padus — (i.e. hägg in Swedish), covered with something white and silky. After a closer look, I saw that there were larvae everywhere. The phenomenon was so exceptional, and interesting, that I took some photos with my digital camera. It was a very warm day, 86°F (30°C).

June 17, 2006

Five days later, on June 17, I took more photos, as I discovered that the larvae were spreading to other areas where bird cherry trees grow. The part of Sweden where I live, had not seen any rain between May 30 up to June 17, 2006. The temperature raised above 77°F (25°C) on June 3. On June 17, it was 81°F (27°C). Such weather supports the life of a larva.

June 20, up to July 2, 2006

June 20–28 it was rainy, and cool weather. With a temperature below 64°F (18°C) all of the time. Most of the larvae pupated, and fell into deep sleep in this period. One could see lots of colonies with pupae in their protective cocoons. A pupa is an insect in its inactive immature form between larva and adult.

From June 29 up to July 2 the weather was very warm, with a temperature above 77°F (25°C).

July 3, 2006

On July 3, the temperature was 84°F (29°C). When I was walking close to the group of bird cherry trees, I saw that some of the larvae had undergone the metamorphosis into moths, via pupation. In shadowy areas, there still were colonies of pupae. In sunny areas, the moths were ready to fly.

One can enjoy the fact that the bird cherry trees were recovering from the attack of the larvae. The group of trees were developing fresh leaves, already on July 3.

Facts about the larvae

A larva is an active immature form of an insect. The larvae, that I show at this website, are coming from the eggs of the Bird-cherry Ermine mothYponomeuta evonymella — (Linnaeus, 1758). In Swedish this moth is named häggspinnmal.

A moth is an insect like a butterfly which is mainly active at night. The female Bird-cherry Ermine moth lays its eggs in the period late summer to fall. The eggs are laid on the fresh branches of the bird cherry tree. The eggs develop the larvae before winter, but the larvae remain in their shells during the winter. When the tree begins to go into leaf, the following year, the larvae burst out from their shells. They feed themselves with the leaves from the tree.

The larvae hold together in colonies, and spin protective cocoons for each separate colony as you can see in some of my photos. The cocoons protect the pupae. A pupa is an insect in its inactive immature form between larva and adult.

The individual larva undergoes the metamorphosis from an immature form, via pupation, to an adult form as a moth sometime in the shift June–July. Then the Bird-cherry Ermine moth is ready to fly in the summer night.

My photos show the larvae as they transform into pupae, and finally are adult insects, Bird-cherry Ermine moths.

Photo 2–3

[Photo 2.] [Photo 3.]
© Photo Conny Andersson 2006

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Conny Andersson
Last modified: September 16 2010