TjCtrva of DeatJis-head Moth. 75 



on the other, they have been supposed by Zaddach to correspond 

 to the inferior or posterior pair of antennary organs of the Crus- 

 taceans, the so-called ' antennae/ whilst the antennae of the imago 

 correspond with the superior or anterior antennary organs or ' an- 

 tennules^ of the Crustaceans. The structures corresponding to the 

 maxillae and labium of such insects as the Coleoptera and Or- 

 thoptera, and to the two pairs of maxillae in Crustaceans, are here 

 more or less fused into a horizontal plate which forms a sort of 

 operculum to the mouth, and carries three segmented organs on its 

 free edge. Of these three organs, the one which is placed mesially 

 is the labium, modified so as to give exit to the common duct of the 

 two silk glands ; and the organs placed one on either side of this 

 ' spinneret ' are the maxillae, modified so as to serve not only in the 

 prehension of food, but also, in many larvae, in the construction of the 

 cocoon. The two pairs of appendages which this compound organ 

 thus represents in the larva, retain more of their typical distinctness 

 in the imago, where they take the shape of a spiral proboscis, and a 

 largely developed and palpigerous labium. On the other hand, the 

 largely developed mandibles of the larva are represented by merely 

 rudimentary organs in the imago, reversing thus the history of the 

 posterior oral appendages. If the eyes be taken as indicating the 

 presence of one segment, the antennae of the larva a second, and 

 those of the imago a third segment, to which three other segments 

 would have to be added for the mandibles, maxillae and labium, the 

 head of the insect will be seen to consist, like that of the typical Ar- 

 thropod, of six segments indicated by as many pairs of appendages ; 

 and the six cephalic segments, together with the three thoracic and 

 eleven abdominal, will make up the entire number of all the seg- 

 ments of the body to twenty. In their possession of prologs and 

 of bright colours upon the integument, the larvae of Lepidoptera 

 differ from those of Coleoptera and Hymenoptera Genuina, which 

 they resemble, as they do also those of the Diptera and Neuroptera, 

 in passing into a state of perfect quiescence a.s pupae. 



For the typical number of segments in the Arthropoda, see Huxley, 

 ' On the Agamic Reproduction and Morphology of Aphis,' 

 Linn. Soc. Trans., vol. xxii., 1858, p. 225. 



For the indication of a distinct cephalic segment which the pre- 

 sence of the eyes furnishes, see Zaddach, Die Entwickelung 



