176 LEAF-MINING INSECTS 



FAMILY NOCTUIDAE 



Of this enormous family a very few species are leaf -miners 

 and these only for a little time while they are small. They 

 soon grow to a size quite too large for the space between the 

 upper and the nether epidermis of a leaf and turn to other 

 habits. It is probable that among the many smaller noc- 

 tuids, the larval habits of which are unknown, other leaf- 

 miners will yet be found. 



Those at present known in our region belong in the allied 

 genera Bellura, Sphida, Arzama and Nonagria, their larvae 

 are rather ordinary tissue-feeding caterpillars of extraordi- 

 nary habits. We will select two of them that have been 

 carefully studied in this country for illustration. 



The cat-tail Arzama, Arzama obliqua, is a miner during 

 its first larval instar in the leaves of Typha latifolia. These 

 leaves are divided lengthwise by a series of IHIII-like par- 

 titions between upper and lower cuticles, forming long 

 channeled interspaces between the Fs, and these channels 

 are crossed by thin partitions of parenchyma cells. These 

 channels are the home of first instar larvae and the cross 

 partitions are their food. From the excellent account of 

 Dr. P. W. Claassen (1921) we condense the following: 



The eggs are laid on the surface of one of the first-formed 

 leaves of T. latifolia, from 6 to 15 inches below the tip. The 

 egg mass is covered with a thick layer composed of a mixture 

 of froth, hairs, and scales from the body of the female. The 

 egg mass resembles a mass of spider's eggs. It is of a dirty 

 yellowish-white color. It measures from 12 to 15 mm. in 

 length, from 7 to 10 mm. in width, and from 3 to 4 mm. in height 

 at the center. In shape it is oblong and convex, the edges gradu- 

 ally thinning out and adhering closely to the surface of the 

 leaf. The long axis of the egg mass corresponds to the long axis 

 of the leaf. Without devouring the egg shell, the embryo breaks 

 through it and bores directly into the leaf of the cat-tail where it 

 works as a leaf-miner. Once the larvae enter the leaf, they begin 



