Rediscovery of Psectrosema tamaricis (De Stefani, 1902) (Diptera, Cecidomyiidae) in Italy and redescription of the species

Abstract

The gall midge Psectrosema tamaricis (De Stefani, 1902) described under the genus Rhopalomyia Rübsaamen, 1892 was found in Palermo, Sicily, near the type locality more than 100 years after the original description; this species induces galls on Tamarix gallica and T. tetrandra (Tamaricaceae). Gagné (1996) in the revision of the genus Psectrosema recorded 26 valid species all associated with Tamarix (Tamaricaceae) from the Mediterranean region to Central Asia and as far as China. Observations on biology and information on the species distribution, illustrations and diagnosis for immature stages, adults and galls, useful for redescription, are provided. Adults of P. tamaricis with one segmented palpus, clublike, coalesced last antennal flagellomeres, long pulvilli, empodia narrow, barely wider than pulvilli. Pupae with a short pupal prothoracic spiracle and lack of spines on the abdomen. Psectrosema tamaricis is similar to P. album and P. nigrum; however, P. album has a small lobe on the lower pupal frons and tarsal claws each with small tooth while P. tamaricis does not have a small lobe on the lower pupal frons and the tarsal claws are simple; P. nigrum has a pigmented pupal abdomen, tarsal claws each with small tooth and spatula broadens below the anterior teeth while P. tamaricis does not have a pigmented pupal abdomen the tarsal claws are simple and the spatula does not broaden below the front teeth. The galls consist of a swelling of the terminal parts of the branches, initially green then purplish-brown; frequently the apical portions of the scaly leaves incorporated in the galls protrude on its surface. The larval chamber is large and elongated, and over time the galls take on a woody consistency, leading to desiccation of the terminal part of the twig concerned. The adults emerge from December until mid-April often leaving the exuvia protruding from the emerging hole and the galls remain on the plant for several years after the gall inducer emergence.