56 [Miirch, 



as a help towards distinguishing these small foi-ms the following table 

 has been drawn up : — 



1. Male with seventh ventral seo-nient produced in a sharp ang-lo in middle. 



a. Larger, paler, with antennae longer and only slightly darker at apex 

 than at base, and with fourth joint as long as broad ; median lobe 

 of male aedeagus bifid at apex .exilis Er. 



h. Smaller, darker, antennae shorter and more distinctly darkened at 

 apex, fourth joint broader than long ; median lobe of male aedeagus 

 simple at apex exillima Shp. 



2. Male with seventh ventral segment only slightly sinuate, not produced in 



a shai'p angle in middle. Intermediate in size, much darker in colour, 

 with antennae decidedly fuscous at apex, fourth joint as long as broad ; 

 median lobe of male aedeagus simple at apex exiliformis Joy. 



M. exilis is always a comparatively large, broad, and pallid insect ; 

 it has the antennae only slightly darkened at apex, and longer than in 

 either of the other two species. 



M. exiUima is much narrower and more obscurely coloured ; the 

 antennae are shorter, and more decidedly darkened towards apex. 



M. exili/oriiiia is intermediate in size and much darker in colour, 

 with the antennae fuscous at apex ; the legs are also usually darker 

 than in either of its allies. 



These descriptions apply to the typical form of each species : but 

 individuals occur in all three in which the elytra are shorter than the 

 thorax, these, when critically examined, generally proving to be males. 

 In all of them the seventh dorsal plate is shorter and slightly more 

 truncate in the males, whilst the seventh ventral plate in the females 

 is longer than the dorsal and rounded at the apex. The females, too, 

 differ inter se, in the shape of the small chitinous spermatheca. 



The figures of the seventh ventral segment are drawn to scale, 

 and as seen from above with the dorsal plate removed. 



M. exilis. M. exiUima. M. (xiliformis. 



Myrtle View, Windmill Road, 



Headington, Oxon. : 

 February, 1917. 



