Syrphus. 275 



27. Abdominal spots isolated from the side-margin, the 

 junction of each two segments with a small, yellow 



spot at the side-margin 26. euchromus. 



— Abdominal spots going over the side-margin ; small, 



narrow species 27. triangulife.r. 



28. Abdominal spots somewhat triangular, sometimes 

 united in front to a very emarginate band, at the 

 sides their hinder corners are nearest the margin; 



eyes bare 25. auricollis. 



— Abdominal spots more or less semicircular; eyes a 



liltle hairy 28. punctulatus. 



29. Epistoma and frons yellow ; thorax with distinctly 

 yellow sides and generally with yellow spots in front 



of scutellum 30. guttatus. 



— Epistoma with a black middle stripe or quite black ; 

 frons more or less black ; thorax not yellow at the 



sides 30. 



30. Jowls yellow or yellowish; epistomal line not pro- 



duced beyond the central knob 31. 



— Jowls black or at least with a black spot at the 

 lower eye margin; epistomal line reaching to or 



almost to the antennæ 32. 



31. Thorax shining ; anterior tibiæ mainly yellow; basal 

 abdominal spots large, in the female produced to 



the front margin; frontal dust spots large 31, umbellatarum. 



— Thorax dull in the male; anterior tibiæ with at least 

 the apical half darkened; basal abdominal spots 

 small, in the female narrow, not produced to the 



front margin; frontal dust spots small 32. compositarum. 



32. Eyes slightly hairy; epistoma yellow at the sides; 

 scutellum partly yellow-haired ; abdomen in the male 



with three pairs of spots 29. lasiophthalmus. 



— Eyes bare; epistoma black in the male and also 

 very dark in the female; scutellum black-haired ; 



abdomen in the male with only two pairs of spots 33. harhifrons. 



In the above table I have used the common way of dividing the 

 bare-eyed species inlo two groups, according to the shape of abdomen; 

 some species may be doubtful ; thus annulatus and lineola have the 

 abdomen not very ovate, but will easily be known as belonging to 

 the ribesii-^roup; bifasciatus and balteatus are somewhat intermediate, 

 but both species are so characteristic, that they are soon recognised; 

 of the rest only punctulatus and lasiophthalmus and perhaps euchromus 

 may be doubtful ; of these species the two former have slightly pubes- 

 cent eyes, and euchromus is recognised by its abdominal markings. It 

 is thus seen that the said division is somewhat natural. For the rest 



18* 



