Larval head anatomy of Heterogynis penella (Zygaenoidea, Heterogynidae), and a general discussion of caterpillar head structure (Insecta, Lepidoptera)

The internal head anatomy (and the peculiar integumental structure of the epicranial notch region) of Heterogynis penella larvae are described; special attention is paid to the skeleto‐muscular and nervous systems and to the cephalic glands. Transverse ligaments connect the apodemes of the mandibular adductor muscles of both sides and the anterior maxillo‐labial articulations of both sides. The two ligaments are linked to each other by a thin, apparently acellular membrane. An accessory, trilobed mandibular gland is present. A putative stretch receptor, connecting the oblique dorsal cibarial dilators of both sides, is described for the first time in a lepidopterous larva and its importance in assessing the homology of these muscles is discussed. The presence of cibarial sensilla, previously predicted in other caterpillars on the basis of behavioural experiments and observations of the nerve pattern, is confirmed. The structural diversity of larval head anatomy in ditrysian Lepidoptera is discussed, with particular emphasis on the innervation of the corpora cardiaca and corpora allata and of the sensilla of the head capsule.