Soft Wax Scale Insects

Soft wax scale insects in the genus Ceroplastes. Click to enlarge.

The little white puffs in the photo don't look like it, but they are insects -- soft wax scale insects. If you pull one off its branch you will see a little gelatinous body under the waxy dome. They remind me of jelly-filled after dinner mints.

Whatever side you look at, wax scales are somewhat featureless. Identifying them often requires magnification, and might require chemical treatment and then mounting on a microscope slide for examination. Another way to identify one is to extract and sequence its DNA; the International Barcode of Life maintains a growing library of DNA reference sequences to identify organisms by comparison. Another clue you can use to identify one is the plant it is eating; they are host specific, that is certain scales eat certain plants.

The scales in these photos are attached to the twigs by tiny strawlike mouths. They suck plant fluids, sometimes so much that they drip sugary liquid from their bodies. Some wax scale species are all female and reproduce parthenogenetically, while others have short-lived males. Females overwinter as we see them in these photos.

If a concerned gardener does not come by and pick them off this plant, the scales will lay eggs that will remain concealed under them until hatching. The hatchlings, called "crawlers" are mobile. They walk on their tiny legs to a new spot, insert their little beaks, and start sucking plant juice and growing waxy coats. Crawlers are sometimes distributed by wind or by unwitting passing animals and birds. In some species, the crawlers settle first on leaves, feed until late summer, and then move to twigs or stems.

The USDA has a website about scale insects called Scale Net. Click here if you have a scale you are wondering about, or if you'd just like to see a few.