UC Davis

Cicadas have amongst the longest development times and are also amongst the largest insects. Cicadas feed exclusively on xylem fluid, which is nutritionally dilute and difficult to obtain. One possible explanation for their slow development is that poor nutrition limits their growth rate. An analysis of 30 cicada species with known development times is consistent with this hypothesis as species with more equatorial distributions grew more rapidly than those at higher latitudes. A second possible explanation is that prolonged development maximizes net reproductive rate because there is little risk of mortality once early instar cicada nymphs establish feeding sites. Extended development probably allows nymphs to store resources and produce more offspring. Spittlebugs also feed obligately on xylem fluid and grow at similarly slow rates although they attain small adult sizes. Unlike cicadas, spittlebugs do not have steep survivorship curves and have shorter development times. The life histories of cicadas and spittlebugs are therefore consistent with both hypotheses. Cicada development times may be limited if (1) the risk of nymphal mortality equals increased fecundity associated with prolonging development, (2) fluctuating conditions sometimes favour rapid development times, or (3) host plant quality changes over time and penalizes nymphs that cannot relocate feeding sites.