beetles (Goliathus) situated at the sides of the thorax near the wings. (Insecta, p. 103, Fig. 57.) The internal processes arising from the sternal region have been called _endosternites_. [Illustration: FIG. 101.—Internal skeleton of _Lucanus cervus_, ♂, head: _A_, antenna; _f_, mandible; _d_, mentum; 2, 4, tendons of mandible; _f_, _u_, _t_, parts of the tentorium; 3 _e_, labial muscles. Thorax: 2, prothorax; 3, 4, meso- and metathorax fused solidly together; 3 _r_, acetabulum of prothorax, into which the coxa is inserted; 2 _s_, sternum; 3_t_, acetabulum of mesothorax, 4_r_, of metathorax; 3 _s_, mesothoracic sternum fused with that of the metathorax (4_g_); 4 _s_, apodeme.—After Newport. ] =The acetabula.=—These are the cavities in which the legs are inserted. They are situated on each side of the posterior part of the sternum, in each of the thoracic segments. They are, in general, formed by an approximation of the sternum and epimerum, and sometimes, also, of the episternum, as in Dyticus (Fig. 97, _A_). This consolidation of parts, says Newport, gives an amazing increase of strength to the segments, and is one of the circumstances which enables the insect to exert an astonishing degree of muscular power. TABULAR VIEW OF THE SEGMENTS, PIECES, AND APPENDAGES OF THE THORAX ═══════════════════════╤═══════════════════════╤═══════════════════════ NAME OF SEGMENT │ PIECES (SCLERITES) │ APPENDAGES ───────────────────────┼───────────────────────┼─────────────────────── 1. Prothorax │Pronotum, sometimes │ │ differentiated into │ │Scutum │1st pair of legs │Scutellum │Patagia │Episternum │ │Epimerum │ │Sternum │ │Antefurca │ │ │ 2. Mesothorax │Præscutum │ │Scutum │2d pair of legs │Scutellum │1st pair of wings │Proscutellum │Tegulæ │Episternum │Squamæ (Alulæ) │Epimerum │Peritreme │Sternum │ │Mesofurca │ │Mesophragma │ │Apodemes │ │ │ 3. Metathorax │Præscutum │ │Scutum │3d pair of legs │Scutellum │2d pair of wings │Postscutellum │(Halteres of Diptera) │Episternum │ │Epimerum │