584 



Wm. S. Marshall, 



Probablv no better condition of the wing rudiment after evagina- 

 tion is well started can be had than by an examination of figures 14 

 and 14^-i where the wing rudiment of a larva 15 mm long is shown 

 in both surface view and sections. At either end the rudiment is longer 

 than the peripodial pore so that there are several sections in which 

 no opening to the exterior is seen (Fig. 14^, lower figure). It is here 

 shown that the rudiment is not only elongated but that is is decidely 

 curved, the concavity facing the peripodial pore. This bending of 

 the rudiment continues in the older stages. 



Certain slight differences between the area of the wing rudiment 

 in the two segments at about this stage might be pointed out; these 

 are noticed in a surface view and shown in Text figure IV. This figure 

 represents two views from the meso- and metathoracic segments of 



Text figure IV. 

 Surface view of the area of the wing rudiment of botli the mesothorax, to the left, and the meta- 

 thoracic Segment, to the right; both talien from the same side of one larva. A, anterior; D, 

 dorsal. In the figure from the mesothorax the dark curved piece near the ventral margin which 

 passes out from the area represents the outline of an external piece of chitin which in part inter- 

 feres with the view. Peripodial pore not drawn. x 280. 



the same side of one larva, length not known. The first dissimilarity 

 to be noticed is the different shape of the very dark chitin which is 

 in each represented by a curved piece near the center of the area of 

 the wing rudiment. In both segments this loop is open posteriorly 

 and in the metathorax it is offen represented by two nearly parallel 

 rods which may offen be disconnected in front and thus appear to 

 be two separate pieces. In the mesothorax it always appears as one 

 piece and the dorsal portion is much larger than the ventral. An- 

 other difference, seen in section, is in the greater height in its segment 

 of the rudiment of the mesothorax. These differences are constant 

 and from the shape of the dark cuticular figure one may distinguish 

 these two thoracic segments from each other. 



\\ith the further increase in size the rudiment shifts its position 

 m the peripodial cavity and, in cross section, is seen to be placed more 



