TACHINIDAE OF ORIENTAL REGION 45 



but to which I am unable - for reasons elaborated later in this section - to grant 

 any validity: consequently I treat many generic names based upon Oriental type- 

 species as synonyms of Dexia or Billaea, a course which accounts for the small 

 number of Oriental genera here recognized. 



Before discussing the characteristics of the Oriental Prosenini in more detail 

 it is necessary to explain my use of the generic name Dexia Meigen, as this is not 

 being used in the sense which would be strictly correct under the International 

 Code of Zoological Nomenclature. The confusion currently existing over the name 

 Dexia, in which a few authors use the name in its nomenclaturally correct sense 

 but the great majority continue to use it in its generally understood (but nomen- 

 claturally wrong) sense, is the most outstanding nomenclatural difficulty that still 

 requires resolution anywhere in the Tachinidae. The 'rival' uses of the name 

 Dexia Meigen result in its application to very different taxa that are not considered 

 to be contribal and are only doubtfully consubfamiliar, and the attribution of the 

 name Dexia to two quite different generic concepts has resulted in 'rival' uses of 

 the family-group names Dexiini and Dexiinae that are based upon the type-genus 

 Dexia. 



The difficulty has arisen from the fact that Dexia Meigen, 1826, when described 

 contained 24 rather diverse species, none of which was designated as type-species. 

 In taxonomic practice, however, a refined use of Dexia grew up under which the 

 name became applied to a distinctive genus containing D. rustica (Fabricius) and 

 D. vacua (Fallen) of Europe and subsequently a number of other species. For 

 the great majority of workers this concept has remained the 'correct' concept of 

 Dexia, but it is not the correct use of the name Dexia under the Code because of 

 the valid designation, made by Westwood (1840 : 139), of Musca volvulus Fabricius 

 as the type-species of Dexia - volvulus belonging to a quite different group of 

 Tachinidae from rustica and vacua. For rustica, Westwood (1840 : 140) proposed 

 the genus Dexilla, and this remains the valid name under the Code for Dexia of 

 most authors. To the genus that should correctly be called Dexia under the Code, 

 because of West wood's type-fixation, most authors apply the name Phyllomya 

 of Robineau-Desvoidy. Summarizing these facts the position is as follows: 



Predominant usage . Dexia Meigen Phyllomya Robineau-Desvoidy 



Correct nomenclature . Dexilla Westwood Dexia Meigen 

 (under ICZN Code) 



The mis-use (nomenclaturally speaking) of the name Dexia for Dexilla is so en- 

 trenched and so general, even amongst specialists on Tachinidae, that it appears 

 unlikely that the widespread usage under which the latter is wrongly known as 

 the former (and under which Dexia is wrongly known as Phyllomya) will 

 be abandoned in favour of the nomenclaturally proper use. In these circumstances 

 it appears to me that, in order to prevent continuing and increasing confusion, 

 the ICZN plenary powers should be invoked to resolve the difficulty in favour of 

 maintaining usage of Dexia: this requires the setting aside of Westwood's type- 

 designation and the fixation of rustica Fabricius as the type of Dexia. 



It will take some time to prepare the necessary case and to obtain a decision 



