12. XYLOMYIA 227 



long reddish orange pubescent lamellee which are longer than the seventh 

 segment ; pubescence of the abdomen greyish white about the sides, short 

 inconspicuous and brownish on the disc, and with short pale fringes on the 

 hindmargins. Belly with the basal spot shining through and with the hind- 

 margins yellowish, almost bare. 



Logs with the hind knees rather more conspicuously black. 



Wings, squamse, and halteres as in the male. 



Length about 5 to Ih mm. 



This species varies a little in the amount of ferruginous coloring on the 

 inner side of the antennae which may extend along the base of the 

 flagellum, in the size of the yellowish spot at the base of the abdomen, and 

 in the pale yellow to rufous orange legs and halteres ; a male from 

 Herculesbad has the antennae ferruginous at the base and the apical 

 style distinct though tiny, while the genitalia appear to be smaller. 

 JC. varia has the hind femora without any tiny black spines beneath 

 and has the coxae orange and the antennae much longer. JC. nigritihialis 

 and X. varicolor from the Canaries represent only one species which has 

 the coxae orange, the hind tibiae blackish, and the hind femora slightly 

 serrulate beneath. X caffra Bigot from Sierre Leone is very near X. 

 nigritihialis, but has the antennae nearly all reddish brown and perhaps 

 shorter, the hind femora stouter and more strongly spined, and the hind 

 tibiae less blackish ; it is however possibly only a variety of X. nigritihialis. 

 X. rujiventris Bigot from Natal has the hind femora serrulate beneath on 

 the apical two-fifths; while X. calopodata Bigot from Ternate and X. 

 pallipes Loew from North America also have serrulate hind femora ; but 

 X, joallipcs has entirely yellow humeral knobs besides other more extensive 

 pale markings on the abdomen. 



X. margiriata was introduced to our British lists upon two males taken 

 by me, one at Wicken on July 14, 1875, and the other at Exning (about 

 five miles distant) on August 11, 1882. I always believed (after the 

 experience of breeding X. maculata) that it would be found common on 

 Poplars (Po2)ulus) in at anyrate the Ten district, and the capture of 

 another specimen at Cambridge by Mr F. Jenkinson in 1905 confirmed 

 my belief, so that its discovery^in considerable abundance at Newnham 

 at the end of July 1906 was not surprising; Dr D. Sharp found the 

 puparia in quantities on some old and decaying Lombardy Poplars 

 {Populus pyramidalis), and close by on some felled Walnut (Juylans) 

 trees he took about sixty specimens (all females) in about an hour, while a 

 visit on August 3 enabled me to take plenty of females in a very short 

 tin)e ; on October 22 Dr Sharp informed me that there were plenty of 

 young larvae on the felled walnut logs, and from them he bred in 1907 

 several of both sexes. We evidently still know no more about the habits 

 of the males than we do about those of the imagines of X. maculata. 



3. X. varia Meigen. Thorax without any yellow markings on the 

 disc. Abdomen yellow at the base only. Antennae more than twice as 

 long as the head. Legs (including coxae) all orange ; hind femora scarcely 

 incrassate and not serrulate beneath. 



Kesembling X. marginata but easily distinguished by its 

 yellow coxse. 



