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IV. The Labial and 3Iaxillanj Palpi in Diplera. By Walter Wesche, F.B M.S. 



{Commmiicated by G. Massee, F.L.S.) 



(Plates 8-10.) 



Eead 16th April, 1903. 



xllTHEIlTO only one pair of palpi have been known in Diptera, and these have 

 generally been regarded as homologous throughout the order. They are described as 

 maxillary by Savigny, and this nomenclature has been accepted and adopted by the largo 

 majority of morphologists. 



The mouth-parts in the various families differ much in shape and armature: the 

 GEstridfe have only a few tubercles, while the Tabanidse have a nearly complete organ. 

 The trophi of the Muscidse are considered typical of the order, and Calliphora, on 

 account of its large size and great abundance, has usually been selected for study ; 

 consequently, the rudiments of palpi, absent in Calliphora, but present in a very minute 

 form in Miisca domestica and many species related to it, have escaped notice. The 

 second pair of palpi have been searched for, as Kirby and Spence * mention that Savigny 

 thought he had seen the rudiments of tlie labial palpi in Tabanus f . Westwood gives as 

 a character of the order, "always destitute of labial palpi" \. Later writers who have 

 studied the proboscis in the Muscidae hold similar views. 



Dr. Benjamin T. Lowne worked at Calliphora erythrocephala in the larval, nympli, 

 and imago stages. The subject bas been most exhaustively treated, sections of the 

 various parts having been largely used in his studies. He says § that the disc on the 

 end of the proboscis (presumably the labella) is derived from the first pair of maxilla?, 

 and the palpi present are, " without the slightest doubt, maxillary palpi." 



Kraepelin II, Chatin ^, and Macloskie** are of opinion that the extremity of the 

 proboscis is derived from a fusion of the labial palpi in the median line. Macloskie thus 

 translates Kraepelin : — "The labella which Burmeister and Erichson have shown to be 



* ' Introduction to Entomology,' Letter xxxv. 



t Savigny, in the first part of his ' Me'moires sur les Animaux sans Vertebras,' entitled " Theorie de la bouche," 

 gives a figure of the labium of Tahamis italicus (plate 4, pp. 51-53). A ventral view is given, and the rudiments 

 consist of two minuie tufts of hair, symmetrically placed on slight projections of the labium ("tige "), immediately 

 posterior to the labella. These he calls " vestiges des palpes ?," adding a note of interrogation. I have not 

 seen any preparation of T. italicui, but I cannot find any similar structure in H<rmatoputa phaialis, or in any 

 of the numerous drawings of Tabanus given in H. J. Hansen's ' Fabrica oris Dipterorum.' In Tabanus bromins 

 and in T. sudeticus are tufts of hair on the ventral side of the labium, but no structures suggesting the rudiments 

 of palpi. 



5 ' Modern Classification of Insects,' ii. p. 40(5. § ' Anatomy and Physiology of the Blowfly,' p. 131. 



II " Zur Anatomic und Physiologic des lliissels von Musca,'' in Zeitschr. wiss. Zool. sxxi.x. (1883) pp. 683- 

 719, tt. 40,41. 



IT 'Machoires des Insectes' (Paris, 1897, 8vo, pp. 202). *• Kraepelin 's ' Proboscis of Afasat.' 

 SECOND SERIES. — ZOOLOGY, VOL. IX. 30 



