60 



THE CLASS OF INSECTS, 



Fig. 63. 



that of the young larva, and stand out free from the body. 

 The head is much smaller in proportion to the rest of the 

 body, and bent more upon the breast. 



The Larva (Fig. 62) 

 when hatched is about 

 five hundredths of an 

 inch in length. The 

 head is now free and 

 the antennae stand out 

 free from the front. 

 The thorax has greatly 

 diminished in size, 

 while the abdomen has 

 become wider, and the 

 limbs very long; and 

 the numerous minute tubercles, seen in the preceding stage, 

 have given origin to hairs. The dorsal vessel can now, for the 

 first time, be seen. When in motion, the resemblance 

 to a spider is most striking. The flow of blood to 

 the head, and the return currents through the lacunar 

 or venous circulation along the side of the body were 

 easily observed. The vessels were not crowded with 

 blood disks, the latter being few in number, only one 

 Fig. 64. or two passing along at a time. Two currents, pass- 

 ing in opposite directions, were observed in the legs. 



FIG. 63. Side view of the head of the larva of Diplax before the first moult, c, 

 deciduous tubercles terminating in a slender style; their use is unknown; they 

 have not been observed in the full-grown larva, e, the compound eyes. 1, the 

 three jointed antennae, the terminal joint nearly three times as long as the two 

 basal ones. 2, the mandibles, and also enlarged, showing the cutting edge divided 

 into four teeth. 3, maxillae divided into two lobes : d, the outer and anterior lobe, 

 2-jointed, the basal joint terminating in two setae ; and a, the inner lobe concealed 

 from view, in its natural position, by the outer lobe, d. 4, the base or pedicel of 

 the second maxillre, or labium, the expanded terminal portion being drawn sepa- 

 rately; d and o, two movable stout styles representing, perhaps, the labial palpi; 

 the lobe to which they are attached is multidentate, and adapted for seizing 

 prey; on the right side the two styles are appressed to the lobe, x represents, 

 perhaps, the ligula; but we have not yet studied its homologies carefully: this 

 part is attached to a transversely linear piece soldered to the main part of the 

 labium. y, the llth abdominal ring, with its pair of conical anal styles, z, the 

 last tarsal joint and pair of long slender claws. 



FIG. 64. The pupa of Diplax, having rudimentary rings, in which the eyes are 

 much larger, and the legs much shorter than in the recently hatched larva; in- 

 troduced to be compared with the young larva. Figs. 57-64, original. 



