with the thorax is called the base; the extremity opposite to this is the posterior margin; the anterior or exterior margin, (sometimes called the costa,) is that which is most advanced in flight, lying in the direction of the head, and the interior margin is the one opposite to it. The angles formed by the meeting of these margins are, the anterior angle, formed by the meeting of the anterior and posterior margins, sometimes called the apex or apical angle; the posterior angle, formed by the posterior and interior margins; in the hinder wings this is frequently termed the anal angle.
It may relieve the tedium of descriptive and technical details, which are often unattractive although indispensable elements of knowledge, to allude for a moment to the play of fancy in which authors have indulged in regard to the analogical relations which the wings of insects bear, both to certain bodily parts of other animals, and of insects themselves. Jurine compared them to the wings of birds, and in this he was followed by Chabrier. Latreille, after a laborious investigation, arrived at the unexpected conclusion, that they are true feet, merely modified in their situation and uses! Shortly after, M. Blainville discovered that wings are nothing else than exterior tracheæ, an opinion which Latreille subsequently inclined to adopt. Nearly at the same time, our countryman MacLeay, conceived the notion that they represent four of the legs of the decapod crustacea. Amid this perplexing diversity of opinion, a German naturalist, M. Oken, comes to
