Early evolution of the proboscis of Lepidoptera (Insecta): external morphology of the galea in basal glossatan moths lineages, with remarks on the origin of the pilifers

Previous information on the external galea morphology of primitive Lepidopt era-Glossata is reviewed. Approximately 40 species are newly examined, and scanning electron micrographs are now available for all families of non-dit rysian glossatan moths with a functional proboscis. Principal objectives of the study are the reconstruction of the groundplan features of the probosc is of Glossata, and of the evolution of this organ in higher Lepidoptera. P lesiomorphic characters of the galea of Glossata include a microtrichiated external galeal wall, a non-microtrichiated food groove composed of finely fluted plates, dorsal galeal linking structures ('dorsal legulae') arranged horizontally and multipointed ventral legulae extending from the lower ant erior margins of the food groove plates. Sensory equipment comprises at lea st a few sensilla trichodea (restricted to the external galea wall), and un iporous sensilla basiconica on both the external galea surface and the medi an food groove. Evolutionary trends are primarily identifiable in the linki ng structures and the sensory organs of the galeae. A third type of sensory organ, sensilla styloconica, an additional ('secondary') set of ventral le gulae (arising below the food groove), and pilifers bearing bristles are ap parently groundplan autapomorphies of a clade comprising all non-nepticuloi d Heteroneura. A tightening of the linkage of the galeae and elaborated sen sory equipment, including three types of proboscis sensilla, are interprete d as key innovations in the evolution of a long proboscis adapted for flowe r-probing.