The classification of insects from embryological data
Louis Agassiz · Smithsonian Institution eBooks · 1850
THE various classifications of Insects which have been proposed by zoologists rest either on considerations derived from their external characters and form, and in part from their internal structure, or on the various modes of their development from the egg.The earliest writers on classification availed themselves principally of the number and structure of their wings, to divide the numberless insects into several general divisions, and such an arrangement, as finally adopted by Linnaeus, has prevailed to a great extent, sometimes modified by the introduction of some smaller groups, which have been more generally admitted by English writers than by those of the Continent of Europe.Fabricius introduced an entirely new view of the subject, dividing the insects according to the structure of the organs by which they take their food, and the various structures and degrees of complication of the jaws became the foundation of his system, which he not only applied in a general manner, but worked out in all its details, assigning even to the smaller divisions characters derived chiefly from the peculiar form of those parts.More recently the metamorphosis of insects has been made the foundation of their classification, and they have been grouped according to the extent of the changes they undergo from the egg, and according to the condition in which the young animal remains for a time before it has arrived at its complete perfect growth.According to these views, those insects that are hatched from the egg with a form very similar to the full-grown perfect animal, and which undergo slight or only partial changes during their growth, such as the additional development of wings, or which remain active throughout their metamorphosis, have generally been con- sidered as belonging to one and the same great division, and have been brought together as insects without metamorphosis, or with imperfect metamorphosis.On the other hand, such insects as are hatched from the egg in the form of a maggot, I. Chewing Insects (Mandibulata). II. Sucking Insects (Haustellata).