Packard.] 146 [Nov. 19, 



Similar intermediate stages have been shown by us to exist in the 

 Hymenoptera, Lepidoptera, and Coleoptera, and in other Diptera. It 

 shows that the distinction between the larval and pupal stages are 

 as truly artificial as in the ametabolous insects. 



Fig. 13 is a dorsal view of the three thoracic segments, with the 

 anterior leg attached, and the wings. The segments are very indis- 

 tinctly marked. The prothoracic stigmata are very near together, 

 though so widely separated in the fully formed pupa. Fig. 13 a is a 

 ventral view of the same parts, the parts somewhat distorted; it also 

 represents the wings, and the two hinder pairs of legs, and 13 6 the 

 fore leg; the joints of the legs are clearly indicated. 



The next stage in the pupa of Stomoxys was much farther advanced, 

 the thorax being formed much as in the mature pupa, as also the ab- 

 domen. The body is still much longer than in Fig. 12, the head nar- 

 rower and freer from the body, and the vertex more elongated. The 

 mouth-parts do not reach much beyond the anterior third of the body, 

 while the wings reach only to the middle of the body (the head ex- 

 cluded), and the hindermost legs only reach a little beyond the mid- 

 dle of the body (the head excluded), and a little way beyond the end 

 of the wings. Viewed dorsally, the thorax is much shorter than in the 

 stage represented by Fig. 12, and the scutellum is short and small, 

 being still quite rudimentary. The form of the eyes can just be 

 distinguished, and the antennas can with difficulty be perceived. 



Fig. 12 represents the succeeding stage of the pupa of Stomoxys. 

 which may be said to fairly represent the typical pupa condition of the 

 cycloraphous diptera. At this time the body is pure white, the eyes are 

 unchanged in color, and under low powers there are no traces of hairs 

 to be seen. In this and the following stages the proportion in the 

 length of the wings and legs, and mouth-parts, remains nearly the 

 same. The wings reach to the middle of the abdomen, while the hind 

 legs just pass beyond the tip end of the abdomen. The mouth-parts 

 reach to the second abdominal segment. The eyes and antennas are 

 clearly indicated (the latter not shown in the drawing). The stages 

 beyond differ but slightly, and form exceedingly gradual steps towards 

 the imago. They differ chiefly in the degree of maturity of the tegu- 

 ment and hairs. In one example, in which the sutures are much 

 more distinct than in Fig. 1 2, the body is slightly dusky, but the eyes 

 are beginning to turn rosy around a portion of the edges. The hairs 

 are also apparent. In a more advanced stage the eyes are a deep 

 scarlet, the hairs are brown, the wings and legs are dusky. 



