We must dwell longer on the head. It is generally rounded, compressed in front, longer than it is broad, and furnished with fine or scaly hairs. The important organs of which this part is the seat are the eyes, the antennæ, the palpi, and the proboscis or trunk. The eyes are more or less spherical, surrounded by hairs, and composed of innumerable facettes. Colours are seen on these as various as those of the rainbow. But the colour which serves as a base to all, is black in some, grey in others; then again there are different gold or bronze colours of the greatest splendour, inclining sometimes to red, sometimes to yellow, sometimes to green. On the compound eye of a butterfly as many as 17,325 facettes have been counted. Simple eyes, or stemmata, are moreover observed in certain species, and are generally more or less hidden by scales. The antennæ are situated near the upper rim or border of each eye. Réaumur has pointed out six principal shapes. One terminates in a little _knob_, and belongs to the butterflies. The others are variously shaped, and belong to the moths. Some are prismatic, or like beading. And lastly, others are shaped like feathers. We represent, in Fig. 137, the different forms of the antennæ, which Réaumur collected together in plates 8 and 9 of his fifth Memoir.[46] [46] "Sur les parties extérieures des papillons," tome i., p. 197. The palpi are four in number, two maxillary and two labial. The first are generally excessively small; one can only ascertain their existence by the aid of a strong magnifying glass: the second are in general very apparent, straight, cylindrical, covered with scales, and formed of three joints, of which the last is often very small and sometimes very pointed. They also sometimes bristle with stiff or silky hairs. The trunk is placed exactly between the two eyes. As long as the butterfly does not want to take nourishment, the trunk remains rolled in a spiral. Some are so short, that they scarcely make one turn and a half or two turns; some larger sized make three turns and a half or four turns; lastly, some very long are curled as many as eight or ten times. This is how the butterfly makes use of its trunk: When fluttering around a flower, it will very soon settle on or quite close to it. The trunk is then brought forward entirely or almost entirely unrolled; very soon afterwards it is almost straightened, then directed downwards, and plunged into the flower. Sometimes the insect draws it out a moment after, curves it, twists it a little, and sometimes even curls it partially up. Immediately it straightens it again, to plunge it a second time into the same flower. It repeats the same manoeuvre seven or eight times, and then flies on to another flower. [Illustration: Fig. 137.--Antennæ of Lepidoptera.]