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W. WESCHE ON THE PROBOSCIS OF THE BLOW-FLY, 



Summary. — It has been shown that the two large sub-orders 

 in Diptera, the Orthorrapha and the Cyclorrapha, are charac- 

 terised, in addition to the method of escape from the pupa-case, 

 by the manner in which the mandibles, when absent as separate 



/. 



1. Type of the wing-venation in the Tabanidae The longitudinal veins 

 are thus indicated throughout the figures: a. auxiliary; 1. first 

 longitudinal vein, etc. 



2. Type of the venation in the Anthomyidae (the earlier Muscidae). The 

 homologies of the veins are indicated by the figures. This type 

 shows the tendency in the later families for the venation to simplify 

 and to leave the lower portion of the wing. It will be noticed that 

 in the Tabanidae the wing is completely encircled by a vein (the 

 costal), while in the Muscidae it is only present on the upper side 

 and stops at the fourth longitudinal vein. 



parts, have been incorporated into the structure of the proboscis. 

 The presence of a similar mentum to that found in the Blow-fly 

 (unique in the Brachycera, as far as my observations have gone) 

 in Haematopota, shows that the Tabanidae must be very close to 

 an ancestral form of the Muscidae. 



