74 Descri'ptions of Preparations. 



obvious to the unassisted eye, give the larva somewhat of a vermi- 

 form appearance ; and together with the absence of wings and of 

 the dense scaly covering clothing both wings and body in the adult 

 Lepidopterous insect, put it into sharp contrast with the imago. 

 Each of the three segments immediately posterior to the head carries 

 with them a pair of quinquearticulate legs. The fourth and fifth 

 post-cephalic segments have no appendages, but, like the fiirst and 

 unlike the second and third, are pierced on each side by a re- 

 spiratory foramen known as a ' spiracle^ or ' stigma.' The sixth, 

 seventh, eighth, and ninth segments possess spiracles, and carry 

 sucker-shaped motor organs, armed with spines, which are known 

 as 'pedes spiirii' or ^prolegs.' The tenth and eleventh segments 

 are furnished with spiracles but have no prolegs ; the eleventh 

 carries on its dorsal surface a tuberculate horn characteristic of the 

 family SpJiingiclae, with the exception of a few species, one of 

 which is North American ; and representing the funis of the 

 embryo. Posteriorly to this horn and between it and the tri- 

 angular supra-anal valve are two half-ring-shaped ridges, reaching 

 from the level of the spiracle of one side over the dorsum to the 

 level of the spiracle of the other. They appear to be distinct from 

 the ventrally-placed half-ring which carries the posterior or fifth 

 pair of prolegs, and it is possible therefore that the presence of 

 three segments may thus be indicated posteriorly to the eleventh, 

 whereby fourteen, the typical number of post-cephalic segments in 

 Arthropoda, would be made up. The greater part of the covering 

 of the head is made up by two large scales, the ''j^arietal scales' 

 of Lyonet, the ^procephalic lobes' of Huxley;' the ' Scheitel- 

 platten' of the German authors referred to below, corresj)onding 

 to the ' epicranium' of the imago. Anteriorly a triangular plate, 

 the ^frontal scale' of Lyonet, the representative of the 'labrum' 

 and ' clypeus' of the perfect insect, is interposed between the pro- 

 cephalic lobes. These lobes or scales are each divided into two 

 nearly equal halves by a dark stripe, on the inferior termination of 

 which are to be found the six ocelli. Mesially to the lower part of 

 the area occupied by the ocelli, the parietal scales give articular 

 origin to the antennae, and more mesially again we have on either 

 side the articulation of the mandible. From the position thus held 

 by the antennae of the larva relatively to that of the organs of the 

 mouth on the one hand, and to that of the antennae of the imago 



