Mealybugs and soft scales of the family Pseudococcidae thrive in warm environments, and large infestations can threaten fruit trees, woody ornamentals and some herbaceous perennials. These two are often grouped together because of their similar habit and life cycle, such as the way they suck phloem from plants.
Soft scale insects range from 1/10 to 1/4 inch and have a soft, waxy outer coating that cannot be separated from their body. They have a barnacle-like appearance. Mealybugs have wool-like bodies that are distinctly segmented and are usually covered in wax. Adult female mealybugs are wingless. The males are rarely spotted but are two-winged and have two long tail filaments. They range in size from 1/20 to 1/5 of an inch, and some varieties include the citrus mealybug (Planococcus citri), longtailed mealybug (Pseudococcus longispinus), Madeira mealybug (Phenacoccus madeirensis), Mexican mealybug (Phenacoccus gossypii), miscanthus mealybugs (Miscanthiococcus miscanthi) and striped mealybug (Ferrisia virgata). There are also root mealybugs in the genus Rhizoecus.
Sources: Alabama A&M & Auburn Universities Extension, University of California Statewide IPM Program and NC State Extension