Larval morphology of Heterogynis (Lepidoptera: Heterogynidae)

Abstract

Abstract. The external morphology and chaetotaxy of the larvae of Heterogynidae (Lepidoptera) are described in order to provide information of potential phylogenetic value for the reconstruction of the systematic relationships within the Zygaenoidea. The most outstanding characteristics of heterogynid larvae are their modified habitus during diapause, the presence of an epipharyngeal lamella, the shape of the prothoracic shield, the presence in the first instar of an organ of unknown function on the middorsum of the mesothorax ("Chapman's organ"), the absence of V2, V3 and Va on the head, the absence of V1 on the prothorax and the presence of two primary setae on the inner side of the proleg, the last trait representing an autapomorphy of the family. A number of possible synapomorphies with the Zygaenidae (e.g. presence of cuticular cavities) suggest a close relationship between these two families, but other larval and adult traits are shared only with the "Phaudinae" and limacodid-group families of the Zygaenoidea (viz. absence of V1 on the prothorax with the "Phaudinae", reduced proboscis and absence of ocelli with them all). Nevertheless, a lack of knowledge of the preimaginal instars of species from some zygaenoid families, and of the homology and polarity of given characters of groups within and outside the Zygaenoidea, hamper a thorough comparison of larvae.

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

“…To examine the extent of heterogynid heterochronic development, further anatomical investigations of larvae and adults of both sexes are desirable; in particular, a study of the head would be informative, given the high number of characters observable in this tagma. This paper extends the available observations (Vegliante and Zilli 2004) on the external structure of the larval head of the common species H. penella to internal anatomy.…”

“…It should be noted that the cardinal sclerite (cd) is completely external (Figs 1B,C and 2C). The reported presence of a small cardinal sclerite sending a long apodeme to the hypostoma (Vegliante and Zilli 2004) could not be confirmed upon closer examination. te‐ca ; anterior tentorio‐cardinal muscle. O: proximally on the anterior tentorial arm (medially to n. 5b; Fig.…”

“…While reference can be made to Vegliante and Zilli (2004) for a general account of the external morphology of the larval head of Heterogynis , some enigmatic aspects of the peculiar structure of the epicranial notch and the junction‐line between the head and neck cuticle have now been clarified by examination of serial sections. As Vegliante and Zilli (2004) pointed out, the larval head of Heterogynis is devoid of an epicranial suture. The posteromedial region of the head is, instead, formed by a flat pentagonal sclerite (ps, Figs 1A and 2A), anteriorly delimited by a U‐shaped crest (U, Figs 1A and 2A).…”

“…The sclerite ‘fu’, corresponding to the sclerite ‘r’ of Snodgrass (1928), is here considered homologous to the ‘fulcre’ of generalized insects (cf. Moulins 1971); its previous designation as ‘stipital bar’ (Vegliante and Zilli 2004) is incorrect, as the latter term indicates the sclerotized ridge between the maxilla and the labium (in Fig. 2B, it is the large sclerite ventral to ‘fu’, with the insertions of nn.…”

“…Head sensilla are named according to Vegliante and Zilli (2004); in particular, sensilla campaniformia are named ‘pores’ in accordance with the nomenclature commonly used to describe lepidopteran chaetotaxy.…”