carries the organs of locomotion, which consist of two pairs of wings attached to its sides, and three pairs of legs attached beneath, a pair belonging to each of the three segments of which the thorax is composed. On the front of the thorax there are two flap-like organs covered with scales, termed the _patagia_. The _Wings_ vary greatly in shape, but usually they are triangular. The portion of the wing which joins on to the thorax is termed the _base_. The front margin is called the _costa_, the outer margin the _termen_, and the lower margin the _dorsum_, these being described as situated when the wing is extended in flight. The angle between the costa and termen {xii}is called the _apex_, and the angle between the termen and the dorsum the _tornus_ (see Plate I., fig. 1). The termen and dorsum are edged with a fringe of hair-like scales, termed the _cilia_. At the base of the hind-wings is generally situated a stiff bristle, or several stiff hairs, called the _frenulum_, the ends of which pass through a chitinous process on the under side of the fore-wing near the dorsum. This process is termed the _retinaculum_, and serves, in conjunction with the frenulum, to lock the wings together during flight. In the female both these organs are often very imperfectly developed, the frenulum consisting of several bristly hairs, and the retinaculum of a group of stiff scales. In many of the _Lepidoptera_ both frenulum and retinaculum are entirely wanting. "In the _Micropterygina_, a membranous or spine-like process called the _jugum_ rises from the dorsum of the fore-wing near the base and passes under the hind-wing, which is thus held between the process and the overlapping portion of the fore-wing."--(Meyrick.) The veins of the wings are thus described by Mr. Meyrick:--