192 LEAF-MINING INSECTS 



stage is very short, averaging about 7 days. When the 

 adult beetles emerge from their pupal skins they are at first 

 white, and the hairs and scales do not yet show their metal- 

 lic hues. Later comes the darkening and the development 

 of iridescence. Her drawings are reproduced herewith. 



Pachyschelus 



The most careful study that has yet been made in this 

 country of a member of this genus is that of Weiss and West 

 (1922) from which we copy the following concerning P. 

 laevigatas: 



The eggs are inserted in a little pocket made usually in the lower 

 surface near the edge of the leaf of Desmodium. The subcircular, 

 nearly flat, jelly-like egg is deposited under a thin layer of tissue. 

 Both the tissue above and below the egg are pushed out slightly and 

 this results in somewhat flat, oval-like blister or swelling which is 

 visible on both leaf surfaces. The tissue over the egg on the 

 lower leaf surface becomes dry and whitish, 'while the upper sur- 

 face of the blister becomes somewhat reddish. 



The mine is started from the egg pocket and later extended in 

 a somewhat irregular and linear manner. By the middle of July 

 most of the larvae are nearly three-quarters grown and by the 

 last of July many are full grown and the mines are completed. 

 On the upper leaf surface the mines appear as dry, brown, irregu- 

 larly linear areas. A few are blotch-like. The number of mines 

 in a leaf varies from one to three, but is usually only one. 



When the greenish larva is full grown it hollows out a circular 

 cavity at the end of the mine. Such cavities are about 5 or 6 

 mm. in diameter. In this place it constructs a circular, somewhat 

 flat, thin, tough, parchment-like cocoon about four millimeters in 

 diameter. These cocoons push out the upper and lower leaf 

 tissues somewhat into comparatively large blister-like swellings. 

 By the first week of August all of the larvae are in these cocoons. 

 At this time the tissue over the linear mines starts to break and 

 this, together with the feeding which takes place earlier in the 

 season, cause the leaves to turn entirely brown and start to curl 

 up toward the midrib. 



