Tergal modifications associated with abdominal glandular cells in the Blattaria.

Tergal abdominal modifications of 30 species of Blattaria (Dictyoptera) were studied by means of histological scanning electron microscopy techniques. Despite marked anatomical diversity of the glands, only a few basic types of cells are present. Male tergal glands which are involved in sexual behavior generally have glandular cells filled with electron transparent vacuoles (type 3a) and those with dense myeloid secretion (type 3b); in addition some have large cells without ducts, not in contact with the cuticle and surrounded by other cells (type 2). External setae, usually associated with these structures, are mechano-receptors or mechano-chemoreceptors. Glands not involved in courtship (e.g., defensive glands) usually have large glandular cells with a ductule that reaches the end apparatus secreted by the glandular cell itself (Type 3) but lack types 2, 3a, and 3b. Species which do not have distinctive tergal modifications may have concentrations of microscopic pores or openings associated with glandular cells on certain segments. The chemistry of the secretions produced by tergal glands is unknown for most species. This paper emphasizes the need for behavioral and biochemical studies to elucidate the biological significance of cockroach tergal glands.