BAGWORM MOTHS OF THE WESTERN HEMISPHERE 139 



foregoing reasons, T. 2)allidovenata is not considered to be a valid 

 species separate from T. e/phemeraejormis. 



Another species which was considered distinct but which has been 

 synonyniized herein is Thyridoj^teryx vernalis. This insect differs 

 from T. ephemerae formis even less than does T. pallidovenata, and, 

 for all purposes, is identical with the former. T. vernalis supposedly 

 represented a spring facsimile of T. ep>hemeraeJormis ] it, therefore, 

 was considered a good biological species since potentially it was iso- 

 lated genetically from the almost exclusively fall-emerging T. ephe- 

 meraejormis. Indeed, if the fact were positively established that 

 T. vernalis was consistently a spring-emerging population or that it 

 had developed genetic barriers against crossing with typical T. 

 ephemeraeformis, the validity of T. vernalis as a species would be more 

 certain. This has not been demonstrated, however, and the avail- 

 able evidence shows that the situation is more nearly the opposite, 

 namely, that T. ephemeraeformis, like T. alcora and especially T. 

 meadi, possesses a life cycle that occasionally may vary. Thus, as 

 now understood by the present author, T. ephemeraejormis is 

 predominantly a fall-emerging insect but one that may be represented 

 by spring adults on certain occasions because of local and scattered 

 environmental changes that modify the life cycle. Many of these 

 spring-emerging specimens probably have no great significance and 

 are not perpetuated because they are isolated individuals. 

 In the warmer coastal and southern areas of this species' range, how- 

 ever, survival through the winter in the larval stage is possible; thus, 

 spring populations are probably able to survive indefinitely. Indeed, 

 after examining the distribution records of T. ephemeraeformis, the 

 writer finds this speculation to be justified. Isolated records from 

 Georgia, Louisiana, Missouri, and Texas indicate the presence of 

 spring and summer males in these areas. Relatively abundant 

 spring material has been noted from Delaware, Florida, and Missis- 

 sippi (in correspondence), evidently representing, in part at least, 

 established populations. However, it is believed that these spring 

 populations, as in the other members of the genus, are not isolated 

 rigidly from the autumn form and that some gene flow does occur 

 between the two seasonal groups because of life cycle fluctuations in 

 both directions. Thus, the spring emerging forms of T. ephemerae- 

 formis are no more entitled to a special name than are the seasonal 

 forms of T. alcora or T. meadi. 



903-052—64- 



