Psaroniocompsa incrustata (Lutz) is an antropophilic species widely distributed in Central and South America. It is the vector of Onchocerca volvulus in a Brazilian focus and has been considered a plague in several areas of this country. The objective of this study was to determine the number of larval instars and to describe the morphological variations and teratologies of a population of P. incrustata from the Pium river, Rio Grande do Norte State. The number of larval instars was determined measuring the head capsule lateral length of 3,164 larvae. The larval instars were determined using the measurement frequency distribution, Student's t-test, the Dyar and Crosby growth rules. Eight larval instars were determined for P. incrustata. A high rate of teratologies (9.6%) in the hypostomium and variations in the lateral serrations and the latero-mandibular process were found.
Larval instar; teratology
