56 CONNECTICUT GEOL. AND NAT. HIST. SURVEY | Bllll. 



optera, by Latreille (1821-1825) and other earlier investigators, such 

 as Kirby and Spence (1826), etc., who interpreted the halteres as ab- 

 dominal appendages, and suggested that the calypteres might represent 

 the true hind wings of the Diptera, The fine investigations of Ham- 

 mond (1881) and Brauer (1882) demonstrated the fallacy of this 

 view, and likewise showed that the interpretations of Westwood 

 (1832) and others who regarded the mesopostscutellum as the ''met- 

 anotum", were incorrect. The scholarly M'ork of Brauer, however, 

 (which involved considerable knowledge of comparative morphology) 

 was entirely ignored in favor of the apparently simple, but morpho- 

 logically unnatural, division of the thorax into regions by Osten- 

 Sacken (188-1), and it is only in comparatively recent times that the 

 real value of Brauer's morphological work ha.s been properly appre- 

 ciated. 



The Metanotum. The metanotum of the Diptera, mtn of Fig. 

 6, A and B, is usually reduced to a narrow, transverse band extending 

 behind the postscutellum, j)sl^ from one halter to the other. It is best 

 developed in the Psychodidae such as Nemopalpus^ Brmchom/yia and 

 Psi/choda, in which the pronotum is as greatly reduced as it is in any 

 of the Diptera (see Crampton, 1926a, Plates 3 and 4). In the pupa 

 of the primitive dipteran Frotoyla^a (Crampton, 1930, Plates 3 and 5), 

 it may readily be seen that the true metanotum arises as it does in 

 other insects, and bears the rather broad wing cases of the halteres. 



The Metayleuron. The metapleuron is fairly large in the myceto- 

 philids (Fig. 6, B) and culicicls (Fig. 6, D) but is frequently greatly 

 reduced in the higher Diptera (Fig. 6, E and F), and may be quitei 

 small even in such primitive Diptera as the tipulids (Fig. 6, A). Thet 

 pleural suture, separating the episternum from the epimeron, extends* 

 from the coxal process (coxifer), c/, to the halter, whose position iss 

 indicated by the label h wdien the halter has been removed. The epi- 

 sternum, es^ (Fig. 6, B and D) is usually somewhat broader than the> 

 epimeron, e-wi, and the latter is sometimes rather closely associated 

 with the first abdominal sclerites. In the tipulid shown in Fig. 6, A," 

 the episternum is divided into an anepisternum. aes^ and katepister- 

 num, hes^ as it is in the mesothorax. 



The anterior extent of the metapleuron is indicated, in a general^ 

 ■way, by the position of the spiracle, sf of Fig. 6, C and D (which is 

 located in the anterior region of the metathorax in the embryo), sol 

 that the location of the spiracle, sy^ mfiy be taken as indicating the* 

 anterior limit of the metapleuron in such Diptera as the sheep tickl 

 shown in Fig. 6, F, in which the posterior portion of the thorax is 

 greatly modified, and is rather closely united with the mesothorax,i 

 etc. The true metapleuron is usually included with the mesothoracici 

 meropleurite, QUfl of Fig. 6, C, in the region called the "hypopleura"' 

 by Osten-Sacken (1884) and others, who prefer a conventional termi- 

 nology to a morphological one; and in such cases, the lateral regioni 

 of the mesothoracic postscutellum, ftg of Fig. 6. B and D, is usually) 

 called the "metapleura". 



The Metasternum. The metasternum is composed of a basister- 

 num and furcasternum in most Diptera, in which the furcasternumi 



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