Labro-Cibarial Sensilla and Armature in Adult Black Flies (Diptera: Simuliidae)

Abstract

A survey of the labro-cibarial sensilla and armature of 26 North American and Australian simuliid species of the genera Gymnopais, Prosimulium, Cnephia, Simulium and Austrosimulium was made using light and scanning electron microscopy. Apical sensilla located at the tip of the labrum are reported for the first time. They are positioned in groups of 3 on either side of the labral tip. In bloodsucking females, each group is situated in a foramen of the sclerotized labral tooth. Labral teeth are absent in males and nonbiting females. Three other groups of sensilla (subapical, lateral and medial) occur on the inner labral surface, and a group in the cibarial pump. Generally, sensillar patterns were similar in the species examined, but the number of sensilla (mainly the lateral group) varied between species, and even between individuals and sexes of the same species. This variation appeared to be related to size of Ayalthough the situation in Prosimulium species needs further study. Nonsensillar structures are present in the cibarium, which in different species range from fine spine combs to large spines and bosses. The internal central plate of the labrum in Austrosimulium mirabile is curved inward as a Aange with a serrated posterior border. Minor differences in sensillar patterns and the differences in cibarial armature appear to be at the species level, rather than at the species-group or generic level.