When the caterpillar has attained its full size, it stops feeding and seeks out a sheltered place—often a chink in a wall. Silken threads are given off by the spinnerets until a little heap of silk is formed into which the hooked end of the abdomen is fixed. Then a girdle of silk is made, passed round the thicker fore-part of the body, and so attached to the wall that the animal is supported in an upright position. The larval skin now splits and is peeled off, and the pupa, or chrysalis, stage (Fig. 225, B) is entered upon. All the external parts of the butterfly are complete at the time of pupation, but profound changes are still necessary in the internal organs; it is to allow these changes to take place in tranquillity that the resting, or pupal, stage is interposed between larval and adult life. At last the new organs are ready for their work, the pupal skin cracks, and the perfect insect (Fig. 225, C) emerges. The head now [Pg 367] carries a pair of large compound eyes, and two slender feelers with knobbed ends. The jaws also have been remodelled in accordance with the completely different manner of life upon which the insect is now entering. The mandibles are now only doubtfully recognisable; the first pair of maxillae are elongated and grooved, and are closely applied to each other to form a long tube called the proboscis (Fig. 226, Mx. 1), which, when not in use for sucking up the sweet juices of flowers, is kept coiled up beneath the head; the palps of the labium (Lab. Pa.) project like tusks on the sides of the head. The thorax is provided with two pairs of broad wings, which are covered with minute overlapping scales—forming a delicate “bloom” which is readily detached by rough handling. In many butterflies and moths the scales are gorgeously coloured and arranged in symmetrical patterns. The name Lepidoptera,[32] which is applied to this order of insects, was suggested by the scaly covering of the wings. When the butterfly is at rest the wings are either fully expanded horizontally, or are held vertically over the back, the upper surfaces of the fore wings being in contact. The first segment of the thorax, which bears the first of the three pairs of legs, is greatly reduced; the third segment also is but small. Fig. 226.—A, Head of a Lepidopterous insect; B, the labium; Ant., feeler; E, eye; Lab. Pa., labial palp; Mx. 1, proboscis; Mx. Pa., maxillary palp (magnified).