8 R. W. CROSSKEY 



large surface area are referred to as 'discal', for example setae standing submedially 

 on an abdominal tergite or on the top of the scutellum (as opposed to round its 

 edge). Setae that bend forwards and downwards in relation to the structure on 

 which they stand are referred to as 'proclinate', those that bend backwards and 

 upwards as 'reclinate', and those that stand out straight from the surface as 'erect'. 

 Setation and hairing of a surface are jointly referred to as the 'vestiture', and when 

 hairing lies down close to the surface it is described as 'recumbent'. The ultra- 

 microscopic pubescence that occurs on many surfaces (and often governs the general 

 appearance of the fly) is termed 'pollinosity' and a structure bearing it is described 

 as 'pollinose' when the pollinosity is visible to the naked eye (these terms being 

 equivalent to the 'dusting' and 'dusted' of some authors). Presence or absence 

 of pollinosity accounts for much of the patterning of the thorax and abdomen: 

 the term 'vitta' is used for a longitudinal band and 'fascia' for a transverse band 

 but the terms do not necessarily imply that the banding is formed by pollinosity. 



In the wing venation cell R 5 is described as 'petiolate' if it is closed well before 

 the wing edge by the coalescence of vein M x with vein A' 4+5 and is connected 

 apically with the wing margin by a definite petiole of the kind shown in Text-fig. 10. 



The figures have been drawn personally and omit needless shading or vestiture 

 that is not significant. Their purpose is to display the essential features that, by 

 supplementing the keys, will ensure accurate identification so far as possible. No 

 attempt must be made to use the figures as a substitute for the keys, even for 

 partial identification, as this will almost certainly result in error because of the 

 frequency with which unrelated tachinids share a closely similar facies. 



A few extra-Oriental genera have been included in some of the generic keys 

 if it seems likely that they will later be discovered within the Oriental region; 

 they have been distinguished by printing their names in non-bold type. Finally, 

 it is strongly emphasized that the keys pertain only to the Oriental species included 

 within the various supraspecific taxa; they will not necessarily work for other zoogeo- 

 graphical regions. 



PRACTICAL IDENTIFICATION AND SUBFAMILY RECOGNITION 



The family Tachinidae is regarded by dipterists as one of the most difficult 

 families of Diptera in which to make practical identifications, despite the relative 

 wealth of characters shown by the adult flies and (taking the family as a whole) 

 the remarkable heterogeneity of form that occurs. The Tachinidae appear to be 

 an evolutionarily young, actively radiating, group and are certainly a group in 

 which acquisition or loss of particular characters in different evolutionary lines has 

 given rise to much confusing resemblance. Few groups of Diptera give more 

 difficulty in classification at the suprageneric level, and a satisfactory arrangement 

 of the Tachinidae into tribes and subfamilies has still not been attained. There 

 is little doubt, however, that a good (that is to say, workable) classification at the 

 tribal-subfamiliar level on the basis of external adult characters never can be 

 achieved because of the frequent lack of close correlation between externally visible 

 adult morphology and the other criteria that seem basic to a phylogenetic classifica- 



