Morphological studies on the head and mouth parts of Leucinodes orbonalis Guenée, 1854. Part I - Mature larva (Lepidoptera: Pyraustidae).

In the head various areas and sutures are deternmined and an attempt is made to clarify the controversy regarding the nature of certain head sclerites. Snodgrass criterion for the determination of the various sclerites on the basis of muscle attachments has been found to be reliable. The so-called "epicranial suture", being of postembryonic origin in the insect, is shown to be the dorsal ecdysial cleavage line. Thus the central triangular area of the head bounded dorsally by the epistomal suture is regarded as the clypeus, while the area dorsal to the epistomal suture is shown to be the frons which has no dorsolateral limits. The structure and morphology of the mouth parts and other head scerites is described in detail. It is shown that contrary to the general belief the larval maxilla bears a prominent galea, besides the palps.