The “rosette-like” structures in the cuticle of Petrobius brevistylis are the openings of epidermal glands

We examined the “rosette-like” structures (RS), found in Archaeognatha and Thysanura, in the compound eyes and the antennae of the machilid Petrobius brevistylis using SEM and TEM. The nature of the RS was unknown until now, and hypothesized to be either a sensillum or the opening of a gland. Our studies show that RS are the orifices of epidermal glands. A gland consists of a single glandular unit of 4 cells: a duct cell, a secretory cell, a ciliary cell and an enveloping cell. The glands are class 3 epidermal glands as defined by Noirot and Quennedey (1974).

► We examined “rosette-like” structures (RS) of machilid Petrobius brevistylis. ► RS were hypothesized to be either a sensillum or the opening of a gland. ► SEM and TEM studies show that RS are the openings of epidermal glands. ► The glands are class 3 epidermal glands ( Noirot and Quennedey, 1974).