The Basal Sclerites of the Leg in Insects. 17 



fectly demarked from the remainder of the coxa in the early stages 

 of development in the Blattidae, thus clearly showing' that it is 

 merely a demarked posterior region of the coxa in these lower in- 

 sects, while in the higher forms, such as the Panorpidae and Di- 

 ptera, the meron becomes secondarily united with the epimeron. On 

 this account, it would be merely reversing the evolutionary sequence 

 to regard the meron as a detached lower portion of the epimeron 

 which has become adherent to the coxa, rather than to regard it 

 as a posterior region of the coxa which has become closely attached 

 to the epimeron in the higher insects. In order to emphasize the 

 fact that the meron is merely a portion of the entire coxa, we have 

 proposed the term merocoxa for the region in question, while the 

 anterior portion of the coxa is designated as the veracoxa. 



In the lower Diptera, such as the Tipulidae (Figs. 14 and 15), 

 the meron me, occupies the characteristic position with reference to 

 the remainder of the coxa, and the same group of muscles are 

 attached to it as are attached to the meron in other insects, yet 

 Bkauer, 1882, calls the meron of the mesothoracic coxae, the "meta- 

 sternum", apparently being misled by Westwood, 1832, who makes 

 a similar mistake in his figure of Tipula (tab. 122), Snodgrass, 

 1909, likewise regards the meron as the posterior region of the 

 sternum (but of the mesothorax instead of the metathorax) in the 

 lower Diptera, and Berlese, 1909, has the same idea concerning 

 the meron of the Lepidoptera, since he terms it the "sternello" 

 (i. e. sternellum) in his fig. 182 and 183 of Sphinx. 



In the higher Diptera (Fig. 11) the meron has united with the 

 lower portion of the epimeron to form the composite region mpl^ 

 which is invariably misinterpreted by all Dipterologists. Thus 

 Hammond, 1880, regards it as the entire epimeron; Petri, 1899, 

 terms it the poststernum (i. e. the posterior region of the meso- 

 sternum); Snodgrass, 1909, designates it as the posterior portion of 

 the sternum (of the mesothorax); Westwood, 1832, Kuenkel d'Her- 

 cuLAis, 1875—1881, Brauer, 1882, Lowne, 1890—1892, Packard, 

 1898, Hewitt, 1907 — 1910, and many others, regard this meso- 

 thoracic region (i. e. mpl of Fig. 11) as the sternum of the meta- 

 thorax; and Osten-Sacken, 1884, together with Williston, 1908, 

 and lany recent Dipterologists, apparently regard it as a portion 

 of the metathorax, which they designate as the "hypopleura". A 

 study of the musculature, however, and a comparison of the sclerites 

 in a series of intermediate forms, clearly shows that the region mpl 



Zool. Jahrb. XXXIX. Abt. f. Anat. 2 



