The Life Cycle of a Scale Insect

Reproduction

• Most scale insects have separate sexes, and reproduction is internal. The female often lays fertilized eggs within her protective wax coating, where they remain until hatching. After hatching, they undergo a series of molts that will eventually lead to the adult scale. In some groups there is hermaphroditism (one individual with both sexes) or parthenogenesis (the development of unfertilized eggs).

Crawlers

• The first instar, which emerges from the egg, is called a crawler, because it moves around the plant where it was born until it finds a suitable new growth into which it attaches its mouth parts and begins feeding. From this moment on, the larvae do not move. The fact that the first instar is the only one to move is reflected in its name. From this point on, males and females follow different pathways.

Female Development

• After the crawler stage, females are not likely to move again. In the first molt, some scale females lose their legs and antennae, while in others they are greatly reduced. While the latter can move around if necessary, this rarely happens. Both types of females molt a second time before reaching maturity and, as all hemimetabolous insects, do not pupate. The adult female retains many external characteristics of the larva, such as the lack of wings (a phenomenon called neoteny), but has functional reproductive organs.

Male Development

• Males undergo two additional molts and emerge as adults with some special characteristics. They have only one pair of wings, which is rare in insects not belonging to the order Diptera (mosquitos and flies). In addition, they do not have mouth parts and do not feed. For this reason, they have very short lives (a day or two). However, they are mobile and are the ones that find the immobile females to mate.

Abundance And Seasonality

• Scale insects are parasites that are present year round, but they are more abundant in the warmer months. They may spend the winter in any stage, but the more resistant ones are the eggs and the mated females (which have not yet laid their eggs). When the temperature rises in the spring and plants start new growth, the eggs begin hatching and the crawlers emerge in large numbers.