350 MR. WALTER WESCHE ON THE GENITALIA OF 



represented by the free, pointed, posterior processes (PI. 23. fig. 4). They are quite 

 evident in Scatopse notata, which has every part complete with the exception of the 

 "spinus tittilatorius " (PL 23. fig. 7). 



Culicidce and Tijmlidie. — In the Culicidse and the Tipulidse they are represented, but it 

 is difiicult to say which are forcipes and which are palpi (PI. 23. figs. 13, 15 ; PI. 24. fig. 23). 



Stratiomi/iidce. — In Beris vallata they appear to be the paired blades springing from 

 the root of the penis (PI. 24. figs. 32, 33). 



Dolichopodidce . — In the Dolichopodidse they can be differentiated from the palpi by 

 their structure (PI. 25. fig. 46). 



Syrphklce. — In Catuhomha pyrastri they take the form of the curious band which 

 encircles the penis (PL 25. fig. 53). In Syritta pipiens they are also much modified and 

 changed into the tAvo strongly chitinized pectinated organs that are on the head of the 

 theca (PL 26. figs. 56, 57). In Eristalls tenax these organs are represented by two 

 curious hooks placed laterally on each side of a chitinous receptacle, which is the orifice 

 of the ejaculatory duct (PL 26. figs. 58, 59). 



Muscidce. — In the Muscidge they are generally present, but not Ln so well-marked a 

 type as in CalUphora, as may be seen by comparing that with Sarcophaga (PI. 26. 

 figs. 60, 68). 



In Glossina palpalis and G. tachinoides they are fused with the " palpi genitalium " 

 (PL 27. fig. 86). 



Ortalidcs and LonchceidcB. — They seem absent in TJlidia nigripennis, but are repre- 

 sented in Lonclicea nigrimana, Meig., which has a similar form of penis. 



Ephydridce. — They are represented in Parydra coarctata and Notiphila nigricornis 

 (PL 28. fig. 98 ; PL 29. fig. 111). 



Homology loith ov/posiior. — There are in the ovipositor of Musca domestica eight single 

 rods and one double rod, fused at the base — besides this, seven or eight transverse setose 

 plates ; and the homology of this part must be sought amongst this rather confusing 

 array *. 



{k) Palpi genitalium. 



Structure. — These are two small, palpiform organs, like the forcipes interiores situated 

 on both sides of the theca but placed anteriorly to them. Sensory hairs and setae are 

 usually present. 



Nomenclature. — Lowne calls the part the " anterior gonapophysis " f, but I prefer the 



* Note. — In the Culicidie I have encountered a special difficulty in homologizing this part, as there are four 

 interior hoots ; these are placed symmetrically in front of the memhrane supported by the lateral processes (PI. 23. 

 fig. 13). These lateral supports are probably the palpi genitalium, and, if that is so, there must be a double pair 

 of forcipes interiores. Those figured as 10 and 12 represent a single pair. 



In J)olic}wj)us festivus there are apparently two pairs of palpi next each other ; they can be differentiated by a 

 curious venation on the head of one pair (PI. 25. figs. 47 & 48). This is a similar difficulty to the previous one, and 

 one which is not easy of explanation. There are many instances of failure of parts, but these two families are the 

 only ones which show a redundance. Mr. Snodgrass, in his paper already alluded to, shows some complicated genital 

 palpi; B. erenatus has several processes at its extremity, and this may be owing to a fusion of the double organ. 



t ' Blow-fly,' p. 740. 



