MACROMIA 165 
and where I have collected for several years. The configuration of 
vegetation and water is a positive factor in determining the course of 
flight.” 
Their flat, long legged, freckled nymphs sprawl on the botton silt, 
which their colors match perfectly. They clamber far out away from 
the water to transform, leaving their empty skins often many meters 
distant from it, attached to tree trunks or walls. 
The nymphs of this genus differ from those of Didymops chiefly in 
that the head is widest across the eyes and slowly narrowed to rear- 
ward. They seem to prefer clayey bottom among the roots of trees 
where a net may hardly be used to get them. 
Nymphs of but three of our species have hitherto been described. 
Their chief characters may be tabulated as follows 
The Known Nymphs 
: Tip of | Ment.| Lat. | Lat. sp.* . 
S Length D bed b 
eee ht ee Horn | Setae | Setae on 9 a ae 
illinoiensis 30 acute | 5+1 6 |straight | Cabot ’90, p. 16 
magnifica 31 acute | 4+1 6 | straight | Cabot ’90, p. 18** 
taeniolata 36 obtuse incurved | Cabot ’90, p. 19 
* Lateral spines. 
** Kennedy (’15, p. 313-322) has adequately described and illustrated this 
species, and has given a key to these nymphs. 
They are of wide distribution, especially in the northern hemisphere. 
About a third of the species occur within our limits. They may be 
distinguished as follows: 
KEY TO THE SPECIES 
Adults 
1 Pale stripe on front of thorax obsolete or nearly so............ 2. 
Pale stripe on front of thorax well developed reaching at least half 
way totehe Crests) cecugeie ts. bs beiagy:, hae. Budeal sadeel Sa 4, 
2 Yellow ring on second abdominal segment divided dorsally..... 
RY iP PER dele Rear ets Pine el deka 1) ahaa See australensis, p. 169 
Yellow ring on second abdominal segment entire.............. 3. 
3 Yellow cross band of abdominal segment 7 in male, reaching lateral 
order... iyo 4 sates cae lel weenie alleghaniensis, p. 167 
Yellow cross band of seventh abdominal segment of male not 
reaching: lateral borders). woes yor oe Ghee illinoiensis, p. 166 
