Modification of cuticular hydrocarbons of Cryptotermes brevis (Isoptera : Kalotermitidae) in response to temperature and relative humidity

To assess their ability to modify cuticular hydrocarbon (CHC) composition a nd survive adverse conditions, Cryptotermes brevis (Walker) nymphs were sub jected to various combinations of temperature and relative humidity. Cuticu lar hydrocarbon profiles of C. brevis were consistent with previous studies . Alkenes were the most prevalent in the CHC mixture, comprising 54.5% of t he total hydrocarbon (n = 12), whereas n-alkanes and branched alkanes compr ised 24.8 and 6.3%, respectively. Sixteen compounds yielded >2% of the tota l hydrocarbon and were subsequently tested for temperature and humidity eff ects in two successive experiments. In both experiments, temperature effect s were found: n-C29 increased and n-C25 decreased with increasing temperatu re. Similarly, five compounds (n-C25, n-C27, n-C29, C39:2, and C41:2) were analyzed for relative humidity effects in experiment 2, based on the result s of experiment 1: only C41:2 indicated a significant positive relative hum idity effect. The remaining 11 compounds comprising >2% of the total hydroc arbon were tested, and a single statistically significant increase was foun d with C45:3 with increasing temperature. Significant positive effects were found with total alkenes, dienes, and trienes; relative humidity had the o pposite effect on total n-alkanes. In both experiments warm, damp condition s were detrimental to survival. Overall, CHC modification was minor; and gi ven that C. brevis has numerous adaptations for dealing with desiccation an d an inability to tolerate high relative humidity it suggests that this spe cies may not vary widely from a highly desiccation-tolerant state.