Common name

Soft scales or coccids

Field characters

The appearance of soft scales in the field is highly variable depending on the group. The body shape is frequently round or broadly oval but some are elongate, especially grass infesting species; they can be nearly flat or highly convex in lateral view. Wax coverings are thin and transparent, filamentous or powdery, thick and opaque, or even thin and glassy. Soft scales occur on nearly all parts of the host but are predominantly found on leaves and stems. Few species are subterranean. Some species produce ovisacs which generally are filamentous and white. Newly matured females can be any of a diverse array of colors from green to brown, mottled to checkered, white to nearly transparent. Old females are usually brown or black. Some species of Coccus are so clear that it is possible to watch the malphigian tubules move inside the body.

Validation characters

Posterior apex of body usually with conspicuous anal cleft; anal area with 2 anal plates; eversible anal ring set at end of anal tube; spiracular atrium connected to body margin by furrow containing wax pores; differentiated spiracular setae set at end of spiracular furrow; tarsus without campaniform sensilla near juncture of tibia and tarsus.

Notes

This family is so diverse morphologically that there are exceptions to most diagnostic characters. For example, Physokemes species lack anal plates; Sythia craniumequinum Kiritshenko lacks spiracular furrows; and Pseudophilippia quantancii Cockerell lacks differentiated spiracular setae. Coccidae Fallén was first used as a family by Samouelle (1819).

Distribution

Soft scales occur in all zoogeographical regions of the world. Click here for a list of genera and species from the Australasian region, Afrotropical region, Nearctic region, Neotropical region, Oriental region, and Palaearctic region. They are most specious in the Palaearctic region; and least abundant in the Oriental region.

Hosts

Soft scales occur on a wide diversity of host plants from woody perennials to herbaceous grasses.

Life history

Soft scales have 3 or 4 instars in the female and 5 in the male. Life history data are highly variable; in the United States many species have a single generation each year, although 2 generations a year is not uncommon. Greenhouse and tropical species can have 6 generations a year. Overwintering occurs in nearly any life stage except the third, fourth, or adult male. In the United States many species overwinter in the second instar or as mated adult females. Most species produce large numbers of offspring; species of Ceroplastes are reported to lay 2,000 or more eggs. In some instances first instars settle on leaves early in the year and move to the stems and branches in late summer or fall. Parthenogenesis is common in soft scales. Second instar males produce a unique test in this family. It usually is semitransparent, glassy in appearance, and is composed of a series of platelike structures.

Important references

Ben-Dov 1993; Borchsenius 1957; Danzig 1980, Gill 1988; Hodgson 1994a; Hodgson & Henderson 2000, 2004; Kosztarab 1996; Kosztarab and Kozár 1988F.

Diversity

Click here for a check list of all coccid genera and species.