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The Ingestion of Xylem Sap by Meadow Spittlebugs, Philaenus Spumarius (L.)

1964; University of Notre Dame; Volume: 71; Issue: 2 Linguagem: Inglês

10.2307/2423300

1938-4238

Richard G. Wiegert,

Forest Insect Ecology and Management

Meadow spittlebug nymphs, Philaenus spumarius (L.), feeding on tomato plants ingested the xylem sap and assimilated the con- tained amino acids. The diet on other plant species is probably similar. Xylem sap provides a dilute, solution of nutrients in a form easy to in- gest and assimilate. The large excess of water associated with this mode of feeding is important in preventing desiccation of the insects. Inges- tion of xylem sap results in a loss of essential nutrients to the plant and a depression of primary production. Consequently, this unusual type of producer-consumer interaction is important in the study of community energetics. Published studies of the biology of meadow spittlebugs, Philaenlus spumarius,2 contain long lists of plant species known to serve as hosts of these sucking insects (see comprehensive bibliography in Weaver and King, 1954), but the specific feeding site and the nature of the ingested food have remained unidentified. My investigation of energy flow in spittlebug populations shows that nymphs ingest the xylem sap of the host plant and subsist on the free amino acids contained in this fluid. The following indirect evidence indicates that xylem sap is the probable food source: (a) Both nymphs and adults produce fluid when feeding. The fluid is expelled from the anus at a rapid rate (as much as 30 mg/hr per mg of insect), and large amounts are produced from a single feeding puncture; (b) Feeding punctures seldom produce necro- sis of the tissue, even when they are concentrated in a small area; (c) If large numbers of nymphs are forced to feed on a short section of stem, the plant parts above the feeding site wilt and eventually die. The bugs will, however, continue to feed from the living stump of the plant; and (d) A paper chromatogram of fresh spittle from a nymph