Observations on the life history and habits of a tropical sawfly, Sericoceros mexicanus (Kirby), (Hymenoptera: Argidae) on Roatán Island, Honduras

Abstract

Observations on the life history and habits of a tropical sawfly, Sericoceros mexicanus, on Roatán Island, Honduras, during January 2002, are reported. This sawfly occurs in southern Mexico and Central America where it feeds on the foliage of Coccoloba spp. On Roatán Island, the only host is seagrape, C. uvifera, a small to medium tree, which occurs on sandy beaches just above tide line. The adults are colourful insects and relatively strong fliers. They swarm around host trees on warm, sunny days and during cool or overcast periods, rest on seagrape foliage and branches. In 2002, a period of peak adult activity occurred between January 8 and10. Eggs are deposited in circular or slightly oval clusters on the undersides of seagrape leaves. Mean egg cluster size is 32.7, range 7–85. Female adults remain with the egg cluster until they die. Eggs hatch within two or three days of oviposition and the larvae feed gregariously on the edges of seagrape leaves, consuming all of the leaf tissue except the major veins. Larvae undergo six instars. However, the small number of instar VI larvae collected suggests that female larvae may undergo an extra instar, as is the case with other species of sawflies. Pupation occurs in parchment-like cocoons attached to leaves, leaf petioles and branches of seagrape. Occasionally, cocoons are attached to wooden surfaces such as picnic benches. A few instar VI larvae were seen with symptoms suggesting virus infection. While heavily infested trees can suffer complete defoliation, the insect appears to cause little or no permanent damage. Local residents regard the insect as a curiosity rather than a pest and report at least two periods of defoliation a year—January and August. Key words: Sericoceros mexicanus, seagrape, Coccoloba uvifera, sawflies, defoliation, tropical forest insects, forest insects