SOME REPRESENTATIVE INSECTS 381 



Europe, Australia, and the Pacific Islands. Correlated with 

 this wide distribution are its great powers of sustained flight, its 

 hardiness, and the wide distribution of the species of the plant 

 upon which it feeds. It is also claimed that the monarch butterfly 

 is not eaten by birds because it has a disagreeable taste, but 

 this has been questioned. The eggs are laid singly upon the 

 leaves of various milkweeds, and in a few days at summer tem- 

 perature, hatch as minute larvae. These feed voraciously and 

 reach their full size in two or three weeks as handsome caterpillars 

 with light-green ])odies conspicuously banded with black and 

 yellow stripes and with pairs of antenna-like filaments toward 

 either end. The molt that closes this larval period produces the 

 so-called chrysalis or pupal stage in which the distinctive adult 

 features, such as wings and antennse, are recognizable in a rudi- 

 mentary state. The chrysahd is attached to the food plant by its 

 posterior end. Although this stage is quiescent to aU external 

 appearance, profound changes are occurring internall}', with the 

 result that after ten or fifteen days the individual molts for the last 

 time and emerges as the adult. The wings are soft and crumpled 

 at first, but they expand and stiffen within a few hours as the butter- 

 fly clings to some neighboring object, and soon the monarch is ready 

 to take its flight. There is one generation a year in the north and 

 two in the south. In the fall the adults are either killed by the 

 cold or wing their way southward to pass the winter as adult butter- 

 flies in sub-tropical regions, passing northward again in the spring. 

 Other butterflies have different seasonal relationships. For exam- 

 ple, some spend the winter in the pupal state, others as eggs that 

 hatch in early spring. 



The moths (Fig. 196), of which there are many species, differ 

 from the butterflies in that the}- fold the wings horizontally 

 and not vertically above the back when at rest, and fly by night 

 instead of by day as do the butterflies. They also differ in the 

 character of their antenna^. Again, the pupal stage of a butter- 

 fly is typically a naked chrysalid attached to some object, while 

 that of a moth is surrounded by a cocoon of silk which is spun in 

 the last larval stage before the molting into the pupa. When the 

 pupal skin is molted within the cocoon of the moth, the adult 

 individual emerges by forcing its way out of the cocoon and, like 

 the butterfly, is ready for flight after the expansion and drying of 

 the wings. 



