Life history and description of the larva of Acrotaeniostola spiralis (Diptera: Tephritidae: Dacinae: Gastrozonini), an Oriental fruit fly inhabiting bamboo twigs

The life history of the bamboo-infesting fruit fly Acrotaeniostola spiralis was studied in northern Thailand. Acrotaeniostola spiralis larvae fed on the apical meristem and surrounding soft tissue of bamboo twigs of Pseudoxytenanthera albociliata. Every infested twig was occupied by one larva. The larva created a feeding tunnel, 32 to 67 mm long and between 0.9 and 3.8 mm wide. Feeding activity of the larva caused the apical leaf of the twig to turn yellow and die. The females deposited their eggs under the margins of rolled apical leaves. The freshly emerged larvae squeezed their way through the folds of these leaves towards the growing point of the bamboo twig. Mature larvae abandoned their feeding sites for pupariation and flies emerged 10-11 days after pupariation. Flies were recorded in the field between the end of April and beginning of December and their larvae between mid-June and beginning of December, indicating that A. spiralis is probably multivoltine. A larva maturing at the end of December remained dormant during the hot season and the fly emerged at the end of April. The external morphology and cephalopharyngeal skeleton of the third instar larva of the genus Acrotaeniostola is described for the first time. The main distinguishing characteristics found for A. spiralis larvae are their very long and slim body shape and their reduced facial mask lacking oral ridges. These are probably adaptations to life in the very narrow bamboo twigs. Bamboo twigs displaying withered apical leaves were sometimes occupied by other flies ( for example, Chloropidae), as well as beetle larvae or caterpillars.