The entomologist's text book : an introduction to the natural history, structure, physiology and classification of insects, including the Crustacea and Arachnida . Tigs. 118, Pronotum—119, Mesonotum—120, Metanotum of a Dyticus. In 118 the subscg-ments are confluent. In 119 and 120 the alternate subsegments are (lotted to show theirextent. We have indeed found a clue for getting out of the difficultyabove mentioned; but from the little attention hitherto paidto the subject, another difficulty of a not less formidable, butof a far more philosophical kind, has presented itself, namely,that of pro
The entomologist's text book : an introduction to the natural history, structure, physiology and classification of insects, including the Crustacea and Arachnida . Tigs. 118, Pronotum—119, Mesonotum—120, Metanotum of a Dyticus. In 118 the subscg-ments are confluent. In 119 and 120 the alternate subsegments are (lotted to show theirextent. We have indeed found a clue for getting out of the difficultyabove mentioned; but from the little attention hitherto paidto the subject, another difficulty of a not less formidable, butof a far more philosophical kind, has presented itself, namely,that of proving, by careful study, the relations of the severalparts in the different orders, and the variations they aresubject to. The total number of parts in the thorax, according to A A 266 ptilota: imago—external anatomy. Audouin, amounts to thii-ty-six; but if the simple pieces, asthe sternum, &c., be supposed to be divided by the medial (Tj (Tj2 (T). 121 i22 •23 Figs. 121, Prostemum—122, Mesosternum—123, Metasternnm of a Pyticus. line, the number will be fifty-two; and Mr. MacLeay, bysupposing that each of the three sterna consists, like theterga, of four transverse pieces similarly divided by the me-dial line, considers the whole number of pieces in the thoraxto mount up to seventy-two. Authors, however, who havelooked at the composition of the thorax, without having anytheoretical views to maintain, have found the really distinctnumber of its parts much fewer in number than either ofthe last-named authors: thus Chabrier and Burmeisterreckon only eighteen, Kirby and Spence twenty, and Strauss-Diiickheim twenty-two. We will now confine our attentionsuccessively to the primary segments of the thorax, andshow the chief modifications which they exhibit, and thendescribe the organs of locomotion. thorax: prothorax. 267 1. The Prothorax {Manitrunk, Kii-by), T 1, upper, and(T) 1, under surface.—This is the segment which imme-dia
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