232 APPLIED ENTOMOLOGY 



of three methods. In the butterflies and some of the moths, the basal 

 portion of the costal region of the hind wing is enlarged, forming a sort 

 of shoulder over which the hind margin of the fore wing lies, thus enabling 

 the two to a large extent, to function as a single wing. In most moths, 

 however, instead of a shoulder, a rather long, curved bristle or cluster of 

 bristles, called a frenulum, arises near the base of the hind wing and runs 

 forward and outward, passing under a small flap or through a tuft of 

 scales on the under side of the fore wing, so that as the two wings move in 

 flight, this frenulum slides backward and forward in its track under the 

 fore wing and holds the two together. A third type of connection, found 

 in only a few moths, is a small lobe near the base of the hind margin of 

 the fore wing, which extends backward toward the hind wing. This lobe 

 is called a jugum and is also probably more or less effective in producing 

 coordination in the use of the wings. 



The number and arrangement of the wing veins is of great importance 

 in the Lepidoptera, much of the classification in this order being based 

 upon these structures. The main veins (see Fig. 20) are of course, 

 longitudinal, starting at the point of attachment of the wing to the body 

 and diverging toward its outer margin, some of them branching several 

 times. Cross-veins are very few, however, and consequently there are 

 only a few closed cells (see page 13), and some at least (perhaps all) 

 of these are produced by the fusion of branches of longitudinal veins, 

 rather than by true cross-veins. 



Various ways of designating the veins and their branches have been 

 offered, but these are best comprehended in connection with laboratory 

 work on the insects themselves, and are therefore not given here. 



The eggs of Lepidoptera vary greatly in form and also in color. 

 They may be elongate, spherical, flattened, scale-like, or of other forms, 

 and the shell or chorion may be smooth or sculptured with ridges and 

 reticulations. The eggs may be laid singly or in clusters and may or 

 may not be covered with hairs from the body of the parent moth, or 

 with a secretion which conceals them from view. They may hatch in 

 a few days or after longer periods, in some cases many months. The 

 adults have no ovipositor so the eggs are always laid on the surface 

 of the place of deposition, though if the abdomen of the insect be small, 

 this may be in a small crack or other opening. 



The larvae produced by the hatching of the eggs are called cater- 

 pillars and have no resemblance whatever to the adults they are to 

 become. They are usually rather worm-like animals, with a generally 

 recognizable head and a body consisting of a series of rather similar seg- 

 ments, the first three of which correspond to the thorax of the adult and 

 almost always bear six legs. Some of the following segments will also 

 have legs but these are totally different in structure from the others and 

 are merely temporary in their nature, designed to support this portion of 

 the body. 



