Description of nymphs and re-description of adults of Callibaetis radiatus Navás (Insecta: Ephemeroptera: Baetidae)

Abstract

The nymph of Callibaetis radiatus Navás (Insecta: Ephemeroptera: Baetidae) is described for the first time based on reared specimens. The following characteristics distinguish the species in the nymphal stage: labium slightly excavated medially; lingua of hypopharynx with three apical lobes; left prostheca robust, apically bifurcate, outer branch robust and with setae on inner margin inner branch slender; femur pale white, with dark gray punctuations anteriorly; tarsal claws with two rows of slender denticles; and arrangement of posterior spines on terga and paraprocts. Male and female adults are redescribed and are distinguished from other adults of Callibaetis by the following combination of characteristics: forewing costal and subcostal area strongly pigmented in females and without pigmentation in males; marginal intercalary veins of forewing mostly single; hindwing transparent, relatively narrow, with apex of costal process truncate and cross veins thicker than longitudinal veins; abdominal color pattern; and first segment of male genital forceps with acute internal process and third segment truncate. The species is reported for the first time from Brazil, thus expanding considerably its known range to the north.