256 Syrphidae. 



or on the apical half. Abdomen with the markings yellow, the bands 

 are broader thari in alneii but narrower than in fasciata, generally 

 occupying a little more than half the length of the segments, the third 

 band not interrupted. Venter as in the preceding species, but the 

 pale parts curiously greyish white pruinose and quite dull. Anterior 

 tibiæ with more or less distinct dark rings and with black and yellow 

 hairs. Wings with the loop of the cubital vein deeper than in alneti, 

 but not fully so deep as in fasciata. Balteres blackish. 



Female. Frons with the black middle line dividing soon after the 

 base as in ahieti, but the legs of the fork not reaching the antennæ, 

 but stopping well above them. Abdomen with the bands slightly 

 narrower than in the male, none of them interrupted and they do not 

 go over the side margin ; the fifth segment with a yellow band or 

 pair of spots. 



Length 9—12 mm. 



D. nitermedia, though in no way common in Denmark, seems to 

 be a little more numerous where it occurs than the other two species, 

 but it has hitherto only been taken on three localities ; Egebæks Vang 

 (the author), Tisvilde (Klocker, the author), and in Jutland at Silke- 

 borg (A. Petersen, Esben Petersen). My dates are ^^/e— ^^/t. I have 

 taken it especially on Hieracium, Matricaria and Jasione. 



Geographical distribution: — Europe down into Austria; towards 

 the north to southern Sweden. 



Remarks: My descriptions of the three species oi Didea are based 

 on a material consisting of 15 specimens af alneti, 39 of fasciata and 

 24 of intermedia, males and females in about equal numbers. I have 

 no doubt that the species are quite good and distinct; they are 

 distinguished by the colour and size of the abdominal markings, and 

 the different depth of the loop of the cubital vein; intermedia is also 

 well distinguished from fasciata by the black line on epistoma and 

 the blackish balteres, and also the curious dull white venter is charac- 

 teristic; when alive it is easily distinguished by the blue thorax. The 

 shape of the frontal stripe of the female is characteristic for all three 

 females, and the female of alneti is distinguished from the two others 

 by the want of markings on fifth abdominal segment; on the other 

 hånd the colour of the hairs on scutellum gives no safe distinction 

 between fasciata and intermedia as black and yellow hairs may be 

 present to the same degree in both species, fasciata has, however, 

 often a quite, or almost quite yellow-haired scutellum, which never 

 seems to be the case in intermedia. Schiner gives as distinction 

 between alneti and the two others three and four bands respectively 

 on abdomen ; it may be supposed that he has only examined females. 



