15 
rank and affinities. The first and higher series has the body usually cylindrical, 
mouth parts more generally formed for sucking ; metamophoses complete, larva 
usually cylindrical, very unlike the adult. The sub-orders embraced by this series 
are Hymenoptera, Lepidoptera, and Diptera. 
The second and lower series, has, usually, the body flattened, mouth parts 
adapted for biting, metamorphoses complete, larva flattened and often resembling 
the adult and comprises Coleoptera, Hemiptera, Orthoptera, and Neurcptera. 
The three regions into which the segments of the six-legged insects are 
grouped, are known by the names of the head, the thorax and the abdomen. 
The head carries the special sense organs, as the eye, the mouth, and the antenne. 
The eyes are wonderful structures, and are constructed to covera very large field of 
vision ; they consist, first of all, of two large compound eyes, made up of numer- 
ous small six-sided facets, which are so numerous that Leeuwenhoec is said 
to haye counted as many as 8,000 in the eye of a fly, and Strauss 8,820 in that of 
a cockroach ; besides these two compound eyes, there are in many insects two or 
more simple eyes (ocelli) arranged across the forehead, they can be easily seen in 
the common Humble Bee. There are some insects which have only ocelli and 
even some with no eyes at all. 
The principal organs of the mouth are six in number, two on each side of 
the opening, one above and one below, the upper single organ is the upper 
lip or labrum, the lower the labrum or lower lip, this lower lip has a basal 
joint (mentum) supporting a more flexible part (ligula); the upper or inner 
integuments of the ligula is usually developed into a kind of tongue, which 
isa distinct part (lingua) in the locusts and dragon flies ; the superior pair of 
the lateral organs are the upper jaws or mandibles, which are generally hard 
and serve to tear the food, the inferior pair are the lower jaws or maxille, which 
are generally soft and serve to carry the food to the gullet, to be swallowed. To 
the lower jaws and under lip are attached short jointed processes, called palpi or 
feelers. These oral organs are the same in all insects, although the structure is 
vastly different among those which obtain their food by mastication and those which 
obtain it by suction ; by dissection and comparative anatomy, however, it can be 
shown that they are identical, only greatly modified in form, in both of these 
classes. In biting insects, as beetles, the side pieces are short, far apart, and have 
a horizontal motion, and the upper lip isa flat plate closing the mouth above ; 
with sucking insects as mosquitoes, the same parts are elongated into lancet-like 
organs, are close together, and have a longitudinal motion, and the lower lip at 
the same time is developed into a tube, which encloses them. In Lepidoptera 
the three upper organs are very feebly developed, while the maxillx are elongated 
into a delicate proboscis, the identification of which with the maxille is shown by 
the occasional presence at its base of a pair of minute palpi; the lower lip is 
soldered to the head, but is furnished with a pair of palpi, well developed and 
