Plant lice

Definition

A common name for aphids (family Aphididae), small sap-sucking hemipteran insects that colonize vascular plants and often form dense aggregations on leaves and stems. The term reflects their louse-like appearance and sedentary, colonial habit rather than phylogenetic relationship to true lice (Phthiraptera). In older or regional usage, 'plant lice' occasionally extends to related Sternorrhyncha such as psyllids, though specialists now restrict it primarily to aphids.

Etymology

From the superficial resemblance to lice (Phthiraptera) in small size, clinging behavior, and habit of clustering on host organisms; 'plant' distinguishes their botanical hosts from animal parasites.

Example

A heavy infestation of plant lice on a rose bush can cause leaf curling and honeydew secretion that promotes sooty mold growth.

Synonyms

• Aphids
• greenfly
• blackfly

Related Terms

• aphid
• Sternorrhyncha
• stylet
• honeydew
• Ant-aphid mutualism
• plant bug

Usage Notes

In contemporary entomological literature, 'aphid' is preferred; 'plant lice' persists in agricultural extension and older texts. The term is sometimes ambiguous: some sources historically applied it to psyllids (jumping plant lice) or adelgids, but modern usage increasingly narrows it to Aphididae. Not to be confused with 'plant bugs' (Miridae, a different hemipteran family).