Distribution of the Genus Ervtiiemis " 21 



This series of eleven species, small as it is and with several of its species 

 occupying nearly identical habitats, is so non-committal as to its origin and 

 routes of migration that these will have to be worked out by some less direct 

 method than that of a study of the degrees of specialization of the individual 

 species. The latter method gives results where the group is large and many 

 connecting links remain. 



It is possible that vesiculosa belongs near Group V B and that the loss 

 of the posterior lobe has occurred independently in Groups III and IV. A 

 careful check of the other characters should decide this. 



We have also the problems of the generic rank of Mesothemis and the 

 value of its two forms, coUocata and simplicicoUis. By penis characters alone, 

 Mesothemis is as valid a genus as Lepthemis. In fact, the specialization of 

 the fusion of the lobes of the cornua and the loss of the posterior lobe has 

 gone farther from the Erythemis type that is found in the majority of the 

 Erythemis species than it has gone in the Lepthemis penis. The forms, col- 

 locafa and simplicicoUis, as viewed in the light of recent work by geneticists 

 on other insects, are prol>al)ly good species. Just how nearly homozygous 

 each is under all circumstances will have to wait until a careful study can 

 be made of the two forms where their habitats overlap. 



