The entomologist's text book : an introduction to the natural history, structure, physiology and classification of insects, including the Crustacea and Arachnida . he three follomngsegments compose the thorax, and the remainder become theabdomen in the perfect insect. Dr. Ratzeburg has, indeed,lately published a memoir, endeavom-ing to prove that thetwo first segments of the larva of the aculeate Hymeno-ptera become the head of the imago; but the observations ofthis author, as I have proved more than once, are incorrect,and founded upon very unphilosophical views. In the Monomorphous division
The entomologist's text book : an introduction to the natural history, structure, physiology and classification of insects, including the Crustacea and Arachnida . he three follomngsegments compose the thorax, and the remainder become theabdomen in the perfect insect. Dr. Ratzeburg has, indeed,lately published a memoir, endeavom-ing to prove that thetwo first segments of the larva of the aculeate Hymeno-ptera become the head of the imago; but the observations ofthis author, as I have proved more than once, are incorrect,and founded upon very unphilosophical views. In the Monomorphous division the larvae greatly resemblethe perfect insect, differing chiefly in being entirely destituteof any appearance of the organs of flight. The third seg-ment of the body also does not exhibit the shield-hke scu-tellum which is found in the imago in that situation: herebelong the various tribes of locusts, grasshoppers, andcrickets (fig. 11, larva of the cricket), bugs (fig. 12, larva ofa Pentatoma), tree and frog-hoppers, cockroaches, prayingmantes, &c., constituting the orders Orthoptera, Hemiptera,and Homoptera, as well as some portions of the order iVew-. Toptera. Some of these insects are, however, remarkablefor being destitute of \^dngs in the perfect state, and a diffi-culty thence arises of distinguishing the larva from the sub-sequent states. The variation in their size, and the constant 182 PTILOTA. absence of ocelli, as well as a somewhat less perfectly deve-loped organization of the antennae, and some other parts oftheir structure, may, however, serve to distinguish analogy with the higher animals we might perhaps beinduced to consider, that these insects, which maintain aconstant activity throughout their existence, are much higherin the scale of natiu-e than those species which, like the but-terfly, are subject to so long a period of death-like repose. In the Heteromorphous di\^sion the larva is totally unlikethe perfect insect, being generally more or less v
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Keywords: ., bookau, bookcentury1800, booksubjectcrustacea, booksubjectinsects
