132 THE entomologist's record. 



into a pupa, the wings expand to about sixty times their former area, 

 and the cells, being no longer crowded, lose their spindle shape, and 

 flatten out into a pavement epithelium. 



The chitinous outer cuticula {eta.') of the pupa encloses each wing 

 in a separate sheath (PL iii., fig. 3), exhibits a stratified condition, 

 and is deeply pigmented near its outer surface (PI. iii., fig. 4). A 

 delicate structureless membrane, known as the inner cuticula f eta.", 

 PI. iii., fig. 4), lies between the outer cuticula feta.' j and the hypo- 

 dermis (lidnii.i. At this stage each wing consists of a hollow bag, 

 the wall of which is composed of a single layer of liypodermal cells 

 f lidrm., figs. 3 and 4) which contain large oval nuclei, the latter ex- 

 hibiting chromatin granules arranged near the periphery. One now 

 finds a delicate membrane {)ii}>r. j»:, PL iii., fig. 4) lining the whole 

 interior of the wing-bags. This is the " grundmembran " of Semper 

 (1857), who showed that it was produced by mesenchymatous cells, 

 which applied themselves to the deep surf.ice of the hypodermis, and 

 sent out lateral processes, serving both to connect the cells with one 

 another and to give them a stellate form. These stellate cells secrete 

 an intercellular substance, filling up the interstices of the network 

 formed by them, and this substance, together with the metamorphosed 

 cells that produce it, finally become the thin structureless membrane 

 to which Semper gave the name " grundmembran." This membrane 

 is widely separated from the hypodermis as a whole, and the space 

 between them contains lymph corpuscles in large numbers (Mayer). 

 It appears to be probable that there are communications between the 

 sub-hypodermal spaces and the chief lumen of the wing. At rather 

 regular intervals the " grundmembran " of one wall becomes con- 

 tinuous with that of the other by means of hollow tubes {tb., PL iii., 

 figs. 3 and 4), formed by the folding of the membrane itself. The 

 cavities of these tubes are direct continuations of the sub-hypodermal 

 spaces of the upper and lower walls of the sac. Leucocytes are fre- 

 quently found within the tubes. A slender thread-like prolongation 

 of the hypodermis cells {}»-c., PL iii., figs. 3, 4, 5) extends inward 

 from each cell of the hypodermis to the " grundmembran ;" each cell 

 gives rise to only one, and occasionally a cell is seen without any, 

 process. The wings at this stage are still little more than simple out- 

 pocketings of the general hypodermis of the chrysalis. In fact, in the 

 larva itself the general hypodermis of the body is lined on the inner 

 side by a thin membrane, coincident in relative position with the 

 " grundmembran " of the wings, and where this membrane is stretched, 

 as in PL iii., fig. 9, the hypodermal cells send out processes which are 

 connected with the membrane. This reminds us of the condition of 

 the processes {pre, PL iii., figs. 3 and 4) in the pupa. 



The wings are filled with hnemolymph (blood), and this fluid con- 

 tains blood corpuscles of different shapes {leti\-y.,le%ivy.',leu\-ii.",V\. 

 iii., figs. 3 and 4), some of which are vacuolated {leu'nj.', PL iii., figs. 

 4 and 5) and appear to be corpuscles in the course of degeneration. 

 Mayer supposes that these are the fat cells of Semper. 



About three weeks before the insect will emerge (a less period, of 

 course, in those species in which the pupal period is very short), 

 " certain of the hypodermic cells {cLfriii., PL iii., fig. 5), which occur 

 at regular intervals, begin to be modified. They begin to increase 

 slightly in size, to project a little above the level of thp ordinary hypo- 



