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
Hw. Krenn et Np. Kristensen, 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, ZOOL ANZ, 239(2), 2000, pp. 179-196
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.