Those Frothy Spittlebugs

At one time or another, each of you has probably seen a frothy, spit-like mass attached to the stem of some plant. Often this is the home of the immature spittlebug. The adult, sometimes called a froghopper, is a small insect that might be mistaken for a leafhopper or a small cicada. Throughout its life the spittlebug feeds on the xylem of its host plant, inserting its beak-like mouth parts mechanically into the tissue. Many species have a number of acceptable host plants, seeming to prefer those associated with nitrogen-fixing bacteria. There are about 2400 known species of spittlebug in the world.

The immature insect, or nymph in this case, locates a suitable feeding site on its host plant, orients itself head down and inserts its beak to begin feeding. In order to create its frothy enclosure, the nymph raises its abdomen and excretes a clear liquid which flows down over the back portion of the abdomen and the back legs. The back legs are used to transfer this liquid forward. When sufficient liquid has been excreted, the nymph executes a number of scooping motions with its abdomen, taking air in on the upswing and excreting it into the liquid on the downswing, forming one bubble at a time. Some species produce 70 to 80 bubbles per minute. Eventually, the nymph is hidden away in a frothy mass where it can consume plant juices, safe from desiccation and predators. Older nymphs and nymphs feeding close together create larger spittle masses. As the froth ages, the bubbles become smaller and the liquid less clear. (When touched gently, fresh masses seem gooey while older ones are sticky. On occasion, I have found dead insects stuck in the spittle mass, perhaps attracted by their need for water. )

In general, immature insects grow in stages, shedding their skin at the end of each stage. Insects are very vulnerable to predation or damage during molting and the subsequent hardening of the new skin. Except for the final molt (when an adult emerges), spittlebugs molt within the spittle mass. Both of the species I found life histories for spent between 30 and 42 days as nymphs and passed through 5 stages, or instars, before becoming adults. Relocation to a new feeding site may take place after the new skin has hardened sufficiently. Insects joining existing spittle masses may add more spittle, making them larger.

The frothy enclosure of the immature spittlebug is a unique adaptation. Watch for it in the field.

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Ron Lyons (volunteer 1990-1999)
Chula Vista Nature Center, 1000 Gunpowder Point Drive, Chula Vista, CA 91910-1201