The house-fly, Musca domestica Linn: its structure, habits, development, relation to disease and control . sixth segmentwould naturally be taken for that of the fifth. The Penis (figs. 26, 27) lies internally on the ventral side of 1 Berlese describes a sinistral asymmetrj of the posterior segments, but hisfigures show a dextral asymmetry, a mistake probably in the reproduction of hisfigures which has escaped the authors notice. PENIS 57 the abdomen, dorsal to the ventral arches of tlu fifth and seventhsegments. It is composed of several sclerites. A median sclerite(), the anterior and ve
The house-fly, Musca domestica Linn: its structure, habits, development, relation to disease and control . sixth segmentwould naturally be taken for that of the fifth. The Penis (figs. 26, 27) lies internally on the ventral side of 1 Berlese describes a sinistral asymmetrj of the posterior segments, but hisfigures show a dextral asymmetry, a mistake probably in the reproduction of hisfigures which has escaped the authors notice. PENIS 57 the abdomen, dorsal to the ventral arches of tlu fifth and seventhsegments. It is composed of several sclerites. A median sclerite(), the anterior and ventral edge of which is rcjiighly semi-circulai in outline, forms the body of the penis. This is producedlaterally to form two alar processes; at the bases of these processesthe lateral extremities of the dorsal arch of the eighth segmentarticulate with the body of the penis; the extremities of the pro-cesses are attached to the lateral extremities of the ventral scleritesof the seventh segment, the secondary- forceps. The penis properconsists of a hollow cylindrical tube, the theca, which receives the. Fig. 27. Penis seen from the right side after it has been removed from within theterminal abdominal segments. Inferior apophysis. «/i.;j. Theca of penis. Glans. ^. Superiorapophysis. Other lettering as in fig. 26, etc. ejaculatory duct. The theca articulates with the body of the penisby means of a pair of small chitinous nodules (cornetti ofBerlese); posterior to the attachment the theca is constrictedslightly. Below the aperture of the entrance of the ejaculatoryduct, the theca is produced into a ventrally directed curvedprocess, the inferior apophysis (iap.); above the aperture a shortcylindrical process, the superior apophysis () arises. Theanterior end of the theca is continued as a slightly inflated hyalinestructure, the glans (), at the curved extremity of which theejaculatory duct opens. CHAPTER IV THE INTERNAL STRUCTURE OF THE HEAD AND
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