Dr. Karl Krapelin oyi the Pulicldse. 41 



halteres, these, notwitlistancling Scliiner's assertion to the 

 contrary, are quite recognizable in the sheep-tick, wliile in the 

 Nycteribiida3 they show all gradations down to quite minute 

 points, so that the complete absence of these apparently insig- 

 nificant organs in the Braulldas need not give us any further 

 disturbance. The ventral thoracic appendages, the legs, cer- 

 tainly present but few differences in the group of the Diptera, 

 nevertheless the five tarsal joints which are usually present 

 are not always constant ; and further, other orders of insects 

 sufficiently prove how little importance attaches in general to 

 the number of tarsal joints and the development of the different 

 sections of the legs. 



The developjnental stages of the Diptera do not show a 

 community of type so distinctly as the structural characters 

 just referred to. The larva? are certainly throughout distin- 

 guished by the absence of jointed thoracic limbs, which is of 

 special interest in the case of those forms which live free upon 

 leaves by prey (many larvaa of Syrphidaj) ; but witli regard 

 to the structure of the head, the armature of jaws, and the 

 development of the traclieal system, there are, as is well 

 known, such important differences, that they have been 

 successfully employed for the systematic division of the order 

 into several suborders and sections. Nevertheless even here 

 intermediate grades are not wanting between the different 

 structural characters (witness the variable development of the 

 first cephalic segment) ; nay, in Brauer's* opinion, the family 

 Lonchopteridas may possibly prove to be a perfect transitional 

 group between the Orthorapha and Cyclorapha, so that the 

 multifarious forms of the larvffi at least offer no veto against 

 the unitariness of the stem of the Diptera. The same thing can 

 also be said of the pupo3, which indeed likewise fall under two 

 main types, but are so far brought together by Brauer's inves- 

 tigations, that these furnish a proof that the so-called " tun- 

 pupa?" (obtected pupee) show very different grades of structure, 

 and in many of them the enveloping larva- skin bursts exactly 

 as in the ordinary moulting, and consequently is to be referred 

 simply to a delayed moulting at the close of the larval period. 

 In the latter case, moreover, if the appendages of the segments 

 of the body are not so closely attached to each other and to 

 the body as in the naked and consequently less protected and 

 more easily injured " mummy-pupa3," no important objection 

 against the natural relationship of the two groups can be 

 derived from this circumstance, which evidently results from 



* F. Brauer, ' Die Zweifliigler des Kais. Museums in Wien,' p. 9 

 (Vienna, 1883) ; also iu the Ueulischr. d, math.-naturwiss. lilasse d. 

 k.-k. Akad. d. Wiss. Bd. xlvii. 



