2-Spot Ladybird Beetle

Description:

A carnivorous beetle used as a localised biological control agent against aphids in, for example, greenhouses. Found throughout the holarctic region. It is very common in western and central Europe and North America. The Two-spotted lady beetle was introduced into Australia specifically as a biological control agent.

Habitat:

The two-spotted lady beetle's life cycle starts with eggs that are usually laid in clutches. The larvae hatches from the egg by biting a hole in it. The larvae look very different from the adults: they have elongated, grey, soft bodies with six legs but no wings. They are cannibalistic. Larvae go through four larval stages: by eating they grow and at some point they shed their old skin and appear in a new one in which they can grow more. The last larval stage is approximately the size of an adult beetle. Once it has eaten enough, the larvae attach themselves to a substrate and moult into a pupa. Inside the pupa, the adult develops. Finally the adult ecloses from the pupa. The most familiar form of the two-spot ladybird beetle is the red one with the two black spots. However, there also exists a black form with red spots on it. In addition, there are intermediate forms, but they occur only rarely in nature.

Notes:

In some populations, the majority of the beetles are female. In these populations, 80-90% of the offspring of a female are female. The cause of this anomaly is the presence of symbiotic bacteria living within the gametic cells of the female lady beetles. The bacterium is too large to live in the male gametes (sperm), so the bacterium can be transmitted to the next generation only through female gametes. When it ends up in a male, it will die when the male dies. Therefore, it kills most of the male embryos in the newly laid eggs. These dead embryos then serve as food for their sisters when they emerge from their eggs. This trait is associated with a variety of different bacteria (Wolbachia, Rickettsia, Spiroplasma), which are present in between 0 and 20% of females, depending on locality. The two spot ladybird also carries a sexually transmitted infection in Central and Eastern Europe. The infection is an ectoparasitic mite Coccipolipus hippodamiae that transfers between male and female (and female and male) during copulation. The infection sterilizes female two spot ladybirds, and at some points of the year, up to 90% of adult 2-spots become infected.