10 R. W. CROSSKE ¥ 
genus Winthemia Robineau-Desvoidy). (In the present work it has been impossible 
to come to any definite conclusion about polymorphism or sexual dimorphism in 
hair colour, and nominal species have been treated as valid if their types differ in the 
colour of the pleural hair.) Colour of the parafrontal, genal, postbuccal, coxal, 
femoral, tibial, and ventral and apical abdominal hair has limited value as a specific 
character. Bristles of the chaetotaxy are nearly always black, but some of the 
bristling in a few species of Chrysorutilia is golden red (especially the postalar and 
vertical setae and the postocular setulae); the significance of this abnormal bristle 
colour is not clear. 
CHAETOTAXY AND HAIRING 
Chaetotaxy in general. The most striking feature of the chaetotaxy in the 
Rutiliini is its instability, much of the bristling being less constant in this tribe than 
in other Proseninae and incomparably less constant than in the higher Tachinidae 
(Tachininae and Goniinae). In the Goniinae, particularly, the principal bristles are 
very constant in arrangement and size, and whole tribes may have a uniform arrange- 
ment of many of the setae—for example all the Sturmiini have 3 + 4 dorsocentral 
setae. In the Rutiliini there is not only intraspecific variability among many of the 
setae in their number, but also in their degree of development and differentiation 
from the surrounding hair; there is often also a lack of bilateral symmetry in the 
bristling of individual specimens, and a few species are sexually dimorphic in certain 
of the setae (e.g. median marginal setae present on abdominal T3 in females but 
absent in males). Failure to appreciate the inconstancy of the chaetotaxy led 
Enderlein (1936), working with rather limited material, to erect several untenable 
genera on the basis of supposed chaetotactic differences, and in the case of Hega 
Enderlein (based on male specimens) and Chromocharis Enderlein (based on females) 
to propose genera for the opposite sexes of the same taxa. 
In spite of the variability in the chaetotaxy, and the fact that almost any chaeto- 
tactic character will fail in the occasional specimen, it is none the less the case that 
the chaetotaxy provides some of the most important characters for supraspecific 
classification—and that several of them are essential key characters by which genera 
and subgenera can be readily enough distinguished. The existence, however, of 
isolated specimens showing chaetotactic characteristics which conflict with the 
norm for their nominal taxon has always to be kept in mind (especially as it is 
virtually impossible to cover every conceivable variant in odd specimens in a 
practical key). 
Head chaetotaxy. There are few features of the head setae of use in classification. 
The ocellar setae are normally small or virtually absent and but little differentiated 
from the long hair of the ocellar triangle. The vertical setae are represented only by 
the inner pair, which shows no useful features. The frontal setae are usually very 
small and fine (Text-fig. 3), often little more than short hairs, and frequently the 
two rows of frontals do not meet at the tips; critical examination might yield minor 
specific differences, but there are no obvious taxonomic characters in the frontal 
setae. Proclinate orbital setae are always absent in males and are often extra- 
