LEPIDOPTERA. 331 



operations with tolerable rapidity, it soon reaches its former sta- 

 tion on the tree. These span-worms are naked, or only thinly 

 covered with very short down ; they are mostly smooth, but 

 sometimes have warts or irregular projections on their backs. 

 They change their color usually as they grow older, are some- 

 times striped, and sometimes of one uniform color, nearly resem- 

 bling the bark of the plants on which they are found. When not 

 eating, many of them rest on the two hindmost pairs of legs against 

 the side of a branch, with the body extended from the branch, so 

 that they might be mistaken for a twig of the tree ; and in this 

 position they will often remain for hours together. When about 

 to transform, most of these insects descend from the plants on 

 which they live, and either bury themselves in the ground, or 

 conceal themselves on the surface under a slight covering of 

 leaves fastened together with silken threads. Some make more 

 regular cocoons, which, however, are very thin, and generally 

 more or less covered on the outside with leaves. The cocoons 

 of the European, tailed Geometer (Ourapteryx sambucaria), 

 which lives on the elder, and of our chain-dotted Geometer (Ge- 

 ometra catenaria), which is found on the wood-wax, are made 

 with regular meshes, like net-work, through which the insects 

 may be seen. A very few of the span-worms fasten themselves 

 to the stems of plants, and are changed to chrysalids, which hang 

 suspended, without the protection of any outer covering. 



In their perfected state these insects are mostly slender-bodied 

 moths, with tapering antennae, which are often feathered in the 

 males. Their feelers are short and slender ; the tongue is short 

 and weak ; the thorax is not crested ; the wings are large, thin, 

 and delicate, sometimes angular, and often marked with one or 

 two dark-colored oblique bands. They generally rest with the 

 wings slightly inclined and almost horizontal ; some with them 

 extended, and others with the hind-wings covered by the upper 

 pair. A very few carry their wings like the Skippers. Some of 

 the females are without wings, and are distinguished also by the 

 oval and robust form of their bodies. These moths are most 

 active in the night ; but some of them may be seen flying in 

 thickets during the day-time. They are very short-lived, and die 

 soon after their eggs are laid. 



