2S51 NOCTUID LARVAE— RIPLEY 13 



secondary sutures, comprising the sole endoskeleton functioning as such, 

 the tentorium being not only very vestigeal but to a large extent membran- 

 ous and flimsy. These secondary infoldings will be referred to as para- 

 demes, a term used to designate secondary infoldings in general. 



In the order Orthoptera the pretentorinae are always found at the ends 

 of the fronto-clypeal suture, this being probably the most generalized 

 condition. These invaginations have migrated dorsad along the fronto- 

 clypeal suture for a considerable distance in the aculeate Hymenoptera. 

 A similar specialization has developed in the lepidopterous larva in a 

 parallel manner, the pretentorinae being located on the epicranial arms 

 (Fig. 13) usually nearer to the dorsal end of the front than to the clypeus. 

 It is of interest to recall that the condition of the postgenae in these larvae 

 is also parallelled in important respects by that of adult Hymenoptera. 

 The position of the pretentorinae is not externally marked, since they 

 invaginate at the bottoms of the epicranial parademes, large infoldings, 

 which extend throughout the entire length of the epicranial suture. Each 

 ribbon-like pretentorium extends caudad to a metatentorium, which it 

 joins near the dorsal end of each secondary postgenal suture. The pre- 

 tentoria are usually chitinized for the greater portion of their length. The 

 metatentorina is also located at the bottom of a deep parademe, one of 

 which arises on each side of the ventral portion of the margin of the fora- 

 men. These invaginations are always to be found just mesad of a large 

 tendon which is supported by the parademe. The metatentoria are short 

 and membranous and are located near the dorsal ends of the secondary 

 postgenal sutures. The corpotentorium persists as a fine thread originat- 

 ing just caudo-mesad of the point where the pretentorium and metaten- 

 torium of each side join and extend across the ventral portion of the fora- 

 men between the metatentoria. In the more generalized families it is 

 often thicker and sometimes heavily chitinized. It assumes the appearance 

 of a delicate white thread in the Noctuidae. We are thus amply justified 

 in concluding that the tentorium of lepidopterous larvae is very highly 

 specialized, being not only vestigial, but also unusual in position and form. 



Heavily chitinized parademes extend the entire length of the epicran- 

 ial, fronto-clypeal and secondary postgenal sutures and along the dorsal 

 and lateral portions of the margin of the foramen. The latter parademe 

 is divided on each side by a short suture into a ventral and a dorsal occipital 

 parademe. The ventral ones are the deepest of all of these infoldings, 

 bearing the metatentorinae and the tendons already mentioned. They are 

 the only ones not heavily chitinized. The fronto-clypeal parademe is not 

 so well developed as the others. These secondary structures serve for sup- 

 port and for the attachment of muscles. They have been developed in 

 correlation with the specialization by reduction which is characteristic of 

 the tentorium of lepidopterous larvae. 



