Journal of Insect Behavior, Vol. 13, No. 2, 2000 Influence of Host Pheromone on Egg Parasitism by Scelionid Wasps: Comparison of Phoretic and Nonphoretic Parasitoids R. Bruni, 1 J. Sant’Ana, 2 J. R. Aldrich, 3,4 and F. Bin 1 Accepted September 23, 1999; revised October 27, 1999 The kairomonal activity of the attractant pheromone for the ‘‘spined soldier bug,’’ Podisus maculiventris (Hemiptera: Pentatomidae), was investigated by exposing fresh pentatomid egg masses in field traps with or without synthetic pheromone. Predominantly two parasitoids were recovered from exposed eggs of P. maculiventris and Euschistus obscurus: Telenomus podisi Ashmead (a generalist pentatomid egg parasitoid) and Telenomus calvus Johnson (a phoretic specialist on Podisus eggs) (Hymenoptera: Scelionidae). The incidences of T. podisi from P. maculiventris and E. obscurus eggs placed in pheromone-baited and nonbaited traps were not significantly differ- ent, suggesting that this oophagous wasp does not use the spined soldier bug attractant pheromone as a kairomone. However, T. calvus was reared almost exclusively from egg masses of P. maculiventris placed inside pheromone- baited traps. These results suggest that T. calvus females orient to volatile chemicals emitted by spined soldier bug males as a searching strategy to find areas likely to contain host eggs, in addition to the previously discovered strategy of using the pheromone to guide their phoretic behavior. The data also indicate that T. calvus can distinguish between the egg masses of these pentatomid hosts at close range. 1 Istituto di Entomologia Agraria, Universita ` di Perugia, Perugia, Italy. 2 Departamento de Fitossanidade, Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. 3 Insect Chemical Ecology Laboratory USDA—ARS, Beltsville, Maryland, USA 20705. 4 Correspondence should be sent to Jeffrey R. Aldrich, USDA—ARS, Insect Chemical Ecology Laboratory, Bldg. 007, Rm. 326, BARC-West, Beltsville, Maryland USA 20705; e-mail: jaldrich@asrr.arsusda.gov 165 0892-7553/00/0300-0165$18.00/0  2000 Plenum Publishing Corporation