Armoured scales (Diaspidae) and soft scales (Coccidae or Lecaniidae)
Scales are small to medium insects with extreme sex dimorphism, i.e. males and females are very different as to their shape and size. Often male insects, which are nearly always wingless, cannot be found or they are at least very rare. In these cases there is virgin birth (parthenogenesis). The females never have wings, their body is compact and hardly segmented, they have no antennae and their legs are clearly visible. The bodies of the females are covered with a wax coating protecting them from unfavourable external conditions. During their development cycle the armour, which gives them their name, is formed by cast off maggot, faecal matter and other substances.
Scales lay eggs. The development of the insects may be completed after a few weeks depending on the species, as a result of this many generations develop quickly. The young maggots - the so-called crawlers - are able to move, whereas the adult insects sit on the plant nearly immobile.
Armoured scales on Orchids live on nearly all parts of the plant with the exception of the roots in the substrate. In the beginning they live hidden and are difficult to see. So there is a high risk of passive dispersal. As most species are adapted to high temperatures, considerable potentials have to be expected in imports from tropical and subtropical countries. The major pests on orchids are armoured scales and soft scales.
Armoured scales have a cover-shaped armour which is not connected with the body and can be removed easily. The insects suck the liquid from individual cells, so there are no phloem suckers.