178 LEAF-MINING INSECTS 



made on the inner side of the leaf. As soon as the larvae appear 

 on the surface of the leaf they at once seek shelter, usually con- 

 tinuing down the stem of the plant and crawling behind the sheath 

 of one of the outer leaves. They later become stem borers. 



Claassen in the same paper (1921) gives an account of 

 another related cat-tail borer, Nonagria oblonga, whose 

 larvae are miners through two or three instars, making 

 irregular mines that traverse the I-like partitions and flex 

 and kill the leaf tips. 



The spatter-dock leaf-miner, Bellura melanopyga, is a 

 miner first in the leaf blades and later in the leaf stalks of 

 Nymphaea americana. From the excellent and detailed 

 account of its habits given by Welch (1914), we condense 

 the following: 



Tw t o fairly well defined periods can be recognized, the 

 mining period, which lasts approximately throughout the 

 first two stadia, and the petiole period, which includes the 

 remainder of the larval existence. During the mining 

 period the larva w T orks on the upper side of the leaf. It 

 usually cuts a somewhat circular hole, slightly larger than 

 itself, through the upper epidermis and penetrates into the 

 parenchyma. There is no regularity in the shape of the 

 mine. Sometimes it appears as a winding tunnel with a 

 diameter about twice that of the larva; sometimes it is 

 digitate in appearance, and sometimes it resembles a blotch 

 mine. Holes through the epidermis other than the original 

 entrance may occur anywhere throughout the length of 

 the mine. Mines are easily detected on the surface of a 

 leaf since they soon become whitish in appearance, due to 

 the removal of the chlorophyll-bearing tissue. The inital 

 entrance to a mine is usually surrounded by excrement and 

 a small quantity of finely masticated leaf tissue. 



Even in the very early stages the larvae are active feed- 

 ers. Larvae, 5.5 mm. long, constructed mines 14 mm. long 

 in less than 20 hours. Larvae, 7 mm. long, w T hen transferred 



