palpi; and a lower lip, called the labium, which represents still another pair of jaws joined together; to this joined piece, or labium, are attached a pair of jointed feelers, called labial palpi. In Fig. 68 these parts are shown separated

from the head.

The numberless varieties of mouth-parts, peculiar to different insects, are in reality made up by modifications of the parts above described. Thus, in one group of insects, the mandibles are lengthened out into a piercing-like sting, while some of the other parts are reduced in size, or become almost obsolete. In another group the maxillæ are greatly elongated, with their edges joined to form a tube, while the other parts of the mouth are scarcely to be discerned. In another group the labium is greatly lengthened to form a tongue-like organ for lapping up food, while the mandibles- so big and hard in some insects—are barely perceptible, and of no use to the insect.

Not only, then, do these parts assume different proportions and different shapes in the different groups of insects, but they also vary greatly in being very hard or very soft.

If the pupils will examine the different kinds of insects' wings, taking the front-pair of wings for example, they will find a marked difference between them, some being very large and transparent, as in the dragon-fly, others being hard and opaque, as in the front wings or elytra of a beetle. Compare the broad and brilliant-colored wing of the butterfly with the straight and narrow fore-wing of a common

grasshopper. And yet these are all wings. In a similar way do the mouth-parts of an insect vary.

65. In the head of a mosquito, what appears to be a single sting, by which the animal pierces the flesh and sucks the blood, is in reality composed of long, delicate, threadlike parts, which represent the mandibles, maxillæ, and the tongue, or ligula, which represents a prolongation of the labium. In the bugs the mouth-parts are compacted into a hard beak—the piercer, so called, consisting of mandibles, maxillæ, and labium, the labrum being represented by an acutely triangular piece.

The mouth-parts of a beetle have already been described in general terms. They are represented as separated from the head in Fig. 68, while in Fig. 69 a side-view of another beetle is given in which the mandible shows very prominently, while the labrum, labium, and maxillæ, do not show at all, as they are concealed by the other parts. The maxillary and labial palpi of one side are seen, however.

66. In the butterfly the labial palpus is seen very large and prominent, while the coiled, thread-like tongue represents the pair of maxillæ lengthened and joined, forming a long elastic tube which can be coiled or uncoiled by the insect, and through which it sips the nectar of flowers. In the mouth-parts of a house-fly the parts are soft and fleshy, and united together to form a sort of proboscis; the maxillæ are minute; the maxillary palpi are present as simple jointed appendages; the mandibles are minute, and useless; while the labium is greatly developed, having a broad end which is

divided into two lobes at the extremity, by means of which the fly laps up its liquid food. The insides of these lobes are rough, and the irritation which flies produce when they alight upon the hand is caused by the scratching of these rough surfaces.

FIG. 69.-HEADS OF A FEW INSECTS SEEN FROM THE SIDE, SHOWING MOUTH-PARTS, NAMED.

67. Much more may be learned about the mouth-parts of insects, and the pupils might attempt the separation of the mouth-parts of such insects as the grasshopper, beetle, wasp, and butterfly, sticking these parts, when separated, upon a piece of white card, as shown in Fig. 68.

It will be advisable, also, for the pupils to utilize the broken specimens of insects by selecting the wings of different insects and gluing them upon a card, labeling each one. Different kinds of antennæ might be fastened upon another card, and the legs of some widely-different insects may be arranged in the same way. For example, let them take the hind-pair of legs of a grasshopper and of a waterbeetle. It will be instructive to observe how different these two kinds are, and how admirably one is adapted for jumping, while the other is so perfectly fitted for a paddle. By making comparative collections of this kind the pupils will learn a great deal regarding the structure of insects.

68. The pupils have thus far learned that a true insect has the body divided into regions called the head, thorax, and abdomen; that the head bears the mouth-parts, antennæ, and eyes. The thorax has the legs and wings, while the abdomen has only the caudal or tail appendages, and these are not often apparent. They have also learned that the thorax is made up of three segments, not often plainly marked, while the abdomen is composed of a greater number of segments, in most cases very plainly apparent. As each segment of the thorax is characterized by having attached to it a pair of appendages, and as the head contains a number of appendages, it is believed by many naturalists that an insect's head is composed of a number of segments, so closely merged together, however, as not to be distinguished, except theoretically. As naturalists, however, differ in their estimate of the number, we will leave this difficult problem for more advanced students to study.

CHAPTER X.

GROWTH OF INSECTS.

69. As the study of the growth of an insect, from the egg to maturity, requires some time and considerable care, the different stages of such growth may be described and taught with what examples the pupil may be able to collect. An afternoon may be spent exclusively in collecting the following objects: