NORTH AMERICAN DIPTERA. 



337 



rudimentary ; the basal extension enlarges, or rather elongates, and, 

 as it becomes longer, and the leverage becomes greater, it decreases 

 in bulk, and becomes finally a chitinous rod. At first free, it gradu- 

 ally attaches itself by what must now be considered its apex, but was 

 originally the base, to the base of the lacinia, and, as these disappear 

 iStomoxys) to the labial organ, so that it seems a mere appendage to 

 this i)art, and remains attached to it on separating the structures. 



In a careful preparation of the blow-fly, CalUphora vomitoria, in- 

 tended to bring out the relative situation of the parts viewed later- 

 ally, I was able to show, more 

 clearly than I ever could in a 

 flat preparation, the precise loca- 

 tion of the separate structures. 

 It will be seen that centrally we 

 have the labium, with its united 

 paraglossse, and very distinct, 

 central ligula, attached by a mus- 

 cular hinge to the base of the 

 fulcrum. In front of this labium, 

 and partly enveloping it, are the 

 lacinia, closely united, and form- 

 ing the chitinous front margin of 

 the operculum or medi-proboscis. 

 Attached at the base of this la- 

 cinia is the palpifer, extending 

 free along the sides of fulcrum, 

 and by its muscular attachments 

 elevating the proboscis, so that it 

 rests with the lacinia between the 

 palpi and against the membrane 

 opposite the open front of the 

 fulcrum. In connection with 

 this flexed condition it will be of 

 interest to again refer to the figure (3 b) of Macrodadylus, as sug- 

 gestive of a possible line of development for the fulcrum. 



The palpi in the blow-fly are from the enveloping membrane, 

 supported by a narrow chitinous strip, indicated in the figure by the 

 dotted portion at base. The subgalea forms the posterior or chitinous 

 portion of the operculum, and I can see no divisional suture. At- 

 tached are the galea, reduced to the well known chitinous supports 

 of the labellate development. 



Fig. 21. Mouth parts of Callipheravomitoria 



TRANS. AM. ENT. SOC. XVII. 



(43) 



NOVEMBER, 1890. 



