18 



Fresh-water Biology 



{Continued from page 16) 



33 — Dorsal hooks as long as the segments which bear them. . Leucorhrinia and Dythemis 

 — Dorsal hooks shorter than the segments which bear them Sympetrum 



34 — Abdomen smooth 35 



— Abdominal hairy 38 



35 — Lateral spines very short Paltothemis 



— Lateral spines long 36 



36 — Spines of 8, short : of 9, long Pachydiplax 



— Spines of 8 and 9 both long and similar 37 



37 — Teeth on inner edge of lateral lobe of labium deeply cut Pantala 



— Teeth obsolete Tramea 



38 — Lateral setas 6 • Nannothemis 



— Lateral setae 7 39 



— Lateral setae 8-10 Erythrodiplax 



— Lateral setae more than 10 Sympetrum 



39 — Lateral spines of 9 one fifth as long as 9 Cordulia 



— Lateral spines of 9 one third as long as 9 Dorocordulia 



40 — Lateral setae 0-3 Ladona 



— Lateral setae 5-10 41 



41 — Median lobe of labium evenly contoured Libellula 



— Median lobe of labium crenulate on front border 42 



42 — Lateral setae 8 Orthemis 



— Lateral set£e 10 Plathemis 



43 — Basal segment of antennae as long as all others together 44 



— Basal segment of antennae not longer than other single segments 45 



44 — Median lobe of labium cleft below bases of lateral lobes Agrlon 



— Median lobe of labium cleft only to base of lateral lobes Hetaerina 



45 — Labium spoon-shaped, narrowed in the middle 46 



— Labium regularly tapered backward to middle hinge 47 



46 — Mental setae of labium 5 each side Lestes 



— Mental setae of labium 7 each side Archilestes 



47 — Gills half as broad as long: no mental setae 48 



— Gills not more than one third as broad as long: mental setas present 49 



48 — Lateral setae 1-4 Argia 



— Lateral setae, none (occasionally 1) Hyponeura 



49 — Hind angles of head angulate 50 



— ^Hind angle of head rounded 51 



{Continued on page 20) 



PLATE 6. DRAGONFLY NYMPHS 



Genera Figs. Length 



Celithemis... 10(9) 15-21 



Cordulia 6 22 



Dorocordulia. (6) 20 



Dythemis.... (9) 17 



Erythrodiplax (14) 12-14 



Ladona 8(1) 22 



Leucorhinia. . 9 18 



Libellula 1 22-27 



Mesothemis.. 11 17 



Disir. Waters L.Sei* 



N,E,S static 



N 



N 

 SW 

 E,S 



E 

 E, N 



G 



G 



static 



static 



lotic 



static 



static 



static 



static 



static 



8-9 



7 



7 



10 



8-10 



6 

 10-11 

 5-10 

 8 



Genera 



Nannothemis. 

 Orthemis. . . . 

 Pachydiplax . 

 Paltothemis. . 



Pantala 



Perithemis. . . 

 Plathemis. . . 

 Somatochlora 

 Sympetrum. . 

 Tramea 



Figs. Length Distr. 

 13 10 E, N 



2(1) 

 12 



(12) 

 t5(4) 

 15 



3(1) 



7(6) 

 14 



22 

 18 

 23 

 25 

 IS 

 24 

 26 

 13 



4,4at 25 



SW 



G 

 SW 



G 

 SE 



G 

 E, N 



G 



G 



* L. Set. = t\\Q raptorial setse on the lateral lobe of the labium, within. 



t This is the toothed inner border of the lateral lobe of the labium: compare fig. 4a of plate. 



Waters L. Set 



static 6 



static 8 



static 10 



9 



12-14 



static 

 static 

 static 

 static 

 static 

 static 



15 



10 



6-7 



9-14 



10-11 



