Undescribed Palpi, &c By Walter Wesche. 415 



from its base. I have seen this in Scatophaga, when the insect 

 has used its lancet on prey. 



It is also obvious that if these palpi are feeling organs, that 

 they would come into play when the lancet was ready for action. 

 This was very clearly demonstrated when the labium and hypo- 

 pharynx were raised with a fine needle, for then the palpi also rose 

 at the base, and being of a darker colour than the labium, were 

 easily seen, fig. 8. 



The discovery of these palpi settles the question as to the 

 larger palpi being labial or not, at least in the Muscidae, and also 

 proves that the proboscis is not formed by a fusion of the labial 

 palpi in the median line. These points have been debated at very 

 considerable length between morphologists, as the ordinary nomen- 

 clature agreed with, or differed from their schemes of homologies ; 

 but hitherto no convincing proof has been advanced by either 

 side. Several writers have rejected the idea that the labium is 

 homologous with the proboscis, deriving it, especially the labella, 

 from the labial palpi, fused with the maxillae and mandibles.* 



On the other hand, it may be conceded that the palpi present 

 in Syrphus and Empis. from their situation at the base of the 

 maxilla?, are maxillary, and that the labial have aborted.! 



How much the presence of the four palpi on the proboscis of 

 a Muscid upsets received ideas, may be gathered from the following 

 extracts. 



The late Prof. Westwood in his Modern Classification of Insects, 

 gives as the description of the mouth-parts of the order Diptera, 

 " Mouth antliate, with a fleshy proboscis (labium), forming a canal 

 and enclosing several lancet-like organs varying in number but 

 always destitute of labial palpi." 



Prof. Packard in describing the house fly {Musca domcstica) 

 says, " The mandibles and maxilla? so well developed in the 

 mosquito and other piercing or biting flies, are aborted, though 

 the maxillary palpi are present." 



Mr. B. F. Lowne (The Blow-Fly, p. 130) says, " Kobineau- 

 Desvoidy is the only author who, so far as I know, arrived at 

 conclusions which my researches enable me to endorse, but unfor- 

 tunately he gives no reasons for his statements, which have 

 received little attention. He says, ' The proboscis of the Diptera, 

 in my opinion, is not formed by the lower lip as in the Hymeno- 

 ptera, but by the maxilla;. In the Muscidse it is usually mem- 

 branous, sometimes solid and triarticulate. The more or less 



* Chatin, I.. 'La machoire des Insectes,' Paris, 1897. 



Wedde, H , ' Beitriige zur Kenntniss des Rhynchotenriissels,' Berlin, 1885. 



Krapelin, K.. •' Uber die systematische Stellung der Puliciden,' 1884; 'Zur 

 Anatomie und Physiologie des Riissels von Musca,' 1883. 



f This can be demonstrated by dissection of the larger species in Syrphus. In 

 Helophilus the palpi are attached to the maxillae. 



