42 PAPERS ON ZOOLOGY OF MICHIGAN. 



AA. Front and liind wings dissimilar, held horizontally when at rest. 



Suborder AXISOPTERA 



C. Triangles ot the iroat and hind wings similar, first and second series ot anti- 

 cubitals not coirciding, except the first and another thick one. 



Family Aeshnidae 



CC. Triangles ot the front wmgs, with the long axis of the triangle at right angles 

 to the long axis of the ivings; triangles ot the hind wings with the long axis, 

 coinciaing with the axis of the wing. 



Family Lihellulidae 



Nyinp)i!i. 



A. Last abdominal segment with terminal, ieaf-like gills. 



Suborder ZYGOPTERA 



B. Basal segment ot the antennae much elongated. 



Family Agrionidae 

 BB . Basal segment of the antennae short. 



Family Coenagrionidae 

 AA. Last abdominal segment ending m five, short, spine-like appendages. 



Subordei AXISOPTERA 



C . Labium flat, not concealing the front of the head. 



Family Aeshnidae 

 CC. Labium spoon-shaped, covering most of the front part of the head. 



Family Libellulidae 



FAMILY AGRIONIDAE. 



KEY TO THE GENERA OF AGRIOXIDAE. 



Imagos. 



A. Imagos with wingj ot a rich black or dusky brown color; basal spaces in all of the wings 

 without cross veins. 



Agrion 



AA. Imagos with large red or brown areas at the bases of the wings, if the wings are hyaline,, 

 basal spaces with cross veins. 



Hetaerina 



Nymphs. 



A. Median clett of the median labial lobe extending far below the base of the lateral labial 

 lobes. 



Agrion 



AA. Median cleft of the median labial lobe not extending below the base of the lateral labial 

 iooes. 



Hetaerina 



GENUS AGRION FABRICIUS. 



J magos. 



A. Apical third ot the hind wings black or cloudy. 



^4. aequabile 

 AA. Wings uniformly black or smoky brown. 



A. maculatum 



Nymphs. 



A. Basal segments or the antennae one-third longer than the head is wide. 



A. aequabile 

 AA. Basal segment of the antennae equal to or less than the width of the head. 



A. maculatum 



