292 Journal of Agricultural Research voi. vi, no.s 



the mine through a small hole in the floor of the mine and after crawling 

 about for a varying length of time prepares to make a cocoon in which 

 to pupate. 



COCOON 



The cocoon is almost invariably made on the upper surface along the 

 edge of the leaf or at its very tip. On preparing to make the cocoon the 

 caterpillar first rasps off and eats a patch of the surface layer of cells 

 along the edge of the leaf, about 4 mm. wide and twice that in length. 

 This causes a withering of the tissue and a slight folding over of the edge 

 of the leaf. Then begins the work of spinning silk. First a loose layer 

 of silk threads is spun from a line about 2 mm. from the edge of the leaf 

 to the inner edge of the patch rasped off. Then follows a second layer 

 of threads which are drawn very tight as they are placed. The anterior 

 two-thirds of the body of the caterpillar enters into this work with great 

 energy and force. The caterpillar's silk press must be a strong one. 

 This layer only slightly draws up the edge of the leaf, but after trans- 

 versed bands are used to tie the tight threads in bundles the edge of 

 the leaf is perceptibly folded. At this time a second layer of foundation 

 threads are spun underneath and then the work of drawing tight 

 threads is continued along one end of the future cocoon. In half an 

 hour the leaf edge is half drawn over and the hardest part of the work 

 is completed. After the edge is tied down tightly the inclosed space is 

 thoroughly lined with snow-white silk, so that a very dense semicircular 

 cocoon 8 mm. long is formed. (PI. XXXIII, fig. 12.) 



PUPA 



The mature caterpillar pupates soon after the cocoon is completed. 

 The pupa is about 4 mm. long, exclusive of the antennal sheaths which 

 project fully a millimeter beyond the tip of the body (PL XXXIII, fig, 

 10, 11). The pupa darkens with age, becoming dark brown on the 

 dorsum and yellowish brown on the venter. The leg, wing, and antennal 

 sheaths are all distinct. The pupal period varies from a few days to a 

 week in midsummer. 



MOTH 



The newly-emerged adult on assuming its full splendor is truly a 

 beautiful creature when viewed through a microscope. When left undis- 

 turbed it will stand perfectly still for hours, with the head elevated and 

 the tip of the wings and abdomen lightly touching the surface on which 

 it rests (PI. XXXIII, fig. 2). This is its characteristic pose, and it holds 

 it so perfectly that prolonged exposures for enlargements can safely be 

 made. While in this pose the light flashes from every properly arranged 

 scale as from polished metal, and one who is only familiar with the appear- 

 ance of museum specimens can hardly appreciate the peacock-like 

 splendor of this seemingl}' proud little creature. 



