Biology of Thrypticus truncatus and Thrypticus sagittatus (Diptera: Dolichopodidae), Petiole Miners of Water Hyacinth, in Argentina, with Morphological Descriptions of Larvae and Pupae

Abstract

Abstract The mining flies Thrypticus truncatus Bickel & Hernández and Thrypticus sagittatus Bickel & Hernández (Diptera: Dolichopodidae) are being evaluated as biological control agents for the water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae). The behavior of adults and larvae of these species was studied in the laboratory and in several water courses of the Paraná River basin, Argentina. The larvae feed on sap from feeding points scraped in the vascular bundles in the petioles of E. crassipes. Pupation occurs in a chamber dug near one of the mine’s openings. External morphology of larvae and pupae, larval cephalic skeleton, and tracheal system are described. The pupae of both species have the ventrally flattened profile of the Medeterinae, with a transverse serrate ridge divided by a notch at the apex of the head. The mines, described herein in detail, constitute the microhabitat where the larvae live throughout their development, and obtain food and protection. Both species are active and reproduce on water hyacinth from spring to the end of fall, and overwinter as larvae inside the mines in the petioles. No morphological or behavioral differences were evident between the immature stages of these species, except in the apical ridges of the pupae. Both species seem to occupy the same niche on the plants.