The identification of Anopheles (Nyssorhynchus) rondoni (Diptera: Culicidae) in Mato Grosso, Brazil: an analysis of key character variability

Abstract

A morphological study was made of a population of Anopheles (Nyssorhynchus) rondoni (Neiva and Pinto) from northern Mato Grosso, Brazil. This population usually lacked the primary key char- acter of a dark basal band on hindtarsomere 3, i.e., hindtarsomere 3 was all white as in most other members of the subgenus. It was determined that this species can be recognized instead by the pres- ence of a dark spot on the thorax made up of a large dark prescutellar space that is contiguous with a concolorous central area on the scutellum. A secondary character of a dark area on the costa created by the fusion of the humeral dark, presector dark and sector dark proximal spots is also usually reli- able. Regression analyses comparing the lengths and ratios of the dark bands on hindtarsomeres 2 to those on 3 describe a straight line relationship. This suggests that the “atypical “population is at one end of a character gradient. We propose that in the subgenus Nyssorhynchus individuals that have a long basal band on hindtarsomere 2 are more likely to also have a basal band on hindtarsomere 3. The pupal stage of this species has not been previously described. Reared-associated specimens&m this study show that the pupa can be easily differentiatedtim all other Nyssorhynchus by the relatively stout, usually 2 or 3 branched (I-5) setae 1 and 5 on segments IV-VII.