20 Clarence Hamilton Kennedy 



of Erythemis penes. In comparison with the penes discussed in the above 

 article, the first pecuHarity in the Erythemis penes that strikes one is the 

 'development of a small, chitinized, two-lobed hood over the medial lobes. 

 Apparently, it is a specialization of Erythemis and its near relatives. It 

 appears in all the species except credula, in which species the penis is most 

 like that organ in the less speciaHzed members of Libellula, Sympetrum, etc. 

 As this species has the generalized characters of venation found in Rhodo- 

 themis, we have considered it the most primitive of the American species of 

 the Erythemis series. Even though it lacks this hood, there is no doubt that 

 credula belongs in or next to Erythemis, as it has in a pair of tubercles the 

 homologue of the hood in the other species (see fig. 8). 



The American species, by penis characters, divide into four groups which 

 are exactly equivalent with the groups as outlined by Calvert and Ris on 

 other characters. To these, Rhodothemis rufa may be added as an extra 

 group. In the key I have placed it first as Group I because of its generalized 

 characters. The fifth and largest group is composed of species with penes 

 so much alike that no good characters appear on which to divide them fur- 

 ther, though they seem to fall into two sub-groups on the shape of the abdo- 

 men. The writer would be inclined to call the whole series of five or six 

 groups Lepthemis and would consider the individual groups as subgenera, 

 which could be given generic rank by those who wish to use smaller genera. 

 Lepthemis, for the whole series from Rhodothemis rufa to Erythemis haema- 

 togastra, is no more comprehensive, in the writer's opinion, than Libellula 

 for the series of species included in the latter by Ris and later by the writer. 

 The comprehensive genus would have to be Lepthemis because of the pri- 

 ority in the use of that name by Hagen.*' The groups may be outlined as 

 follows : 



I . Oriental ( Rhodothemis) Group I — rufa 



i'. American (Lepthemis and Erythemis) 2. 



2 (i'). Hood over media! lobes undeveloped (represented by two tubercles) 



Group 1 1 — credula 



2'. Hood over medial lobes developed into an arched two-lobed affair 3. 



3 (2'). Posterior lobe of penis lacking, the three cornua fused into a single conspicu- 



ous, terminal lobe 4- 



3'. Posterior lobe present 5- 



4 (3). Lateral lobes and cornual lobe parallel to the axis of the penis (Lepthemis)... 



Group ni — vesiculosa 



4'. Lateral lobes and cornual lobe bent across the axis of the penis (Mesothemis) . . 

 Group IV — collocata simplicicollis 



5 (3'). Abdomen not especially slender (Erythemis) 



Group 'V A — peruviana mithroides attala 



5'. Abdomen slender (Erythemis) .. .GroupV B — plcbeja carmelita hacinatogastra 



« Synopsis of the Neuroptera of North America, p. 160, 1861. 



