Iiitiodutlion. 7 



it may also be horizontal and ratlier large, as f. inst. in tlie Tipulidæ 

 and Xylophagidæ, especially Xylophagus. The thorax is thus chiefly 

 formad of niesotliorax, the protliorax is very small and also the 

 metathorax; of the latter may sometimes be seen a narrow part 

 behind the postscutellum and between the balteres; on the ventral 

 side sometimes a narrow metathoracic part may also be distinguished. 

 The spiracles I take to be prothoracic and mesothoraeic. 



Abdomen consists of a number of segments of which the last ara 

 generally more or less transformed; in the descriptions I give the 

 number of not transformed segments; these are as a rule not difficuit 

 to see but sometimes one or more of the last may be small or the 

 last may be more or less hidden. Also at the base of the abdomen 

 the first segment may be narrow, and sometimes the first and second 

 ventral segments may be coalesced, yet generally a suture marks the 

 line of connexion. 



The legs are somewhat uniform, only 

 they may be relatively short or on the 

 contrary relatively long, and they may 

 be stronger or weaker. Generally the 

 somewhat sluggish and not well flying 

 Diptera have much stronger legs than 

 those that fly well ; the species with 

 somewhat strong legs often bear bristles 

 on them. The tarsi are five-jointed ; the 

 last joint bears a pair of claws which are ^.^^ j lateral vie^v of thorax of 

 generally smiple, but sometimes may be Dryomyza anilis. 



serrated or otherwise specially formed. 



Besides the claws there are at the end of the last joint still three organs, 

 which may be of some systematic importance: under the claws are 

 attached two lobes, the pulvilli, these are generally organs of fastening; 

 they may be of diflferent, sometimes complicated, forms, and of different 

 sizes, and sometimes they may be absent. Between the pulvilli is 

 inserted a median organ, the empodium ; this may also be very different 

 in form, from quite uniform with the pulvilli to the form of a long 

 bristle, and sometimes it is feathery or of other complicated form ; it 

 may sometimes be absent. — According to de Meijere (Ueber das 

 letzte Glied der Beine bei den Arthropoden, Zool. Jahrb., Abth. fur 

 Anat. und Ont. XIV, 1901) the claws and organs mentioned are not 

 inserted on the fifth joint itseif but on a special small apical joint, the 

 prætarsus. According to him the empodium in the Diptera is not 

 ahvays morphologically of the same origin; in the Tipulidæ f. inst. 

 we have a real etnpodium, but in most of the other Diptera the 



