202 DURHAM DIPTERA. 



XXVIII. 311. 



311. Xylota, Mg. 



1 (6). Abdomen with conspicuous reddish markings. 



2 (5). Legs partly yellowish. 



3 (4). Hind femora equally and obviously spinose; hind 



trochanters of the male with a long spine. 

 1600. Xylota segnis, L. 

 Fairly common everywhere. 



4 (3). Hind femora scarcely spinose at all; male hind 



trochanters almost unarmed. (1601. tarda, Mg.) 



5 (2). Legs all black ; male hind trochanters quite simple. 



1602. Xylota lenta, Mg. 

 Bishop Auckland, i $, 21-6-99. 



6 (1). Abdomen without any reddish markings, but usually 



with yellow or orange spots. 



7 (8). End of the abdomen entirely covered with golden pile. 



1603. Xylota sylvarum, L. 

 Bishop Auckland, 1 $, 4-7-01 ; Harperley, 1 ? , 

 17-7-00; Hesleden, 1 2, 13-8-00. 



8 (7). End of the abdomen in no way conspicuous. 



9 (10). Knees only very narrowly pale ; abdomen with 



distinct quadrate yellow marks ; hind trochanters 

 of the male unarmed ; size 8 mm. 



(1604. nemorum, F.) 



10 (9). Basal third of fore tibiae pale ; hind trochanters of the 



male with a short spur. 



11 (12). Abdomen with yellowish subquadrate markings ; size 



10 mm. (1605. florwn, F.) 



12 (11). Abdomen with small partly yellowish or bluish 



markings ; size 9 mm. 



1606. Xylota ablens, W. 

 Gibbsnees, 1 $ , 4-8-97. 



312. Syritta, St. Farg. 



1607. Syritta p'piens, L. 

 Common everywhere. 



