Species Celastrina ladon - Spring Azure - Hodges#4363
Genomic evidence suggests further changes of butterfly namesBy Zhang, J., Q. Cong, J. Shen, P.A. Opler, N.V. Grishin
Taxonomic Report of the International Lepidoptera Survey, 8(7): 1-41., 2020
Zhang, J., Q. Cong, J. Shen, P.A. Opler, N.V. Grishin, 2020. Genomic evidence suggests further changes of butterfly names. Taxonomic Report of the International Lepidoptera Survey, 8(7): 1-41
Butterflies of Pennsylvania, a field guideBy James L. Monroe, David M. Wright
University of Pittsburgh Press
From the publishers page:
This work has all of the features that make field guides to a region's butterfly fauna useful to anyone with a serious interest in that fauna. . . . the book is a bargain and a must for anyone with an interest not just in Pennsylvania's fauna, but the northeast fauna as a whole.
News of the Lepidopterists' Society
Winner, 2017 National Outdoor Book Award
Though I am in the southeast, I own this field guide and find it very useful - Roy Cohutta Brown.
A Swift Guide to Butterflies of North America: Second EditionBy Jeffrey Glassberg
Princeton University Press, 2017
This is a revised second edition of the most detailed, comprehensive, and user-friendly photographic field guide to the butterflies of North America. Written by Jeffrey Glassberg, the pioneering authority on the field identification of butterflies, the guide covers all known species, beautifully illustrating them with 3,500 large, gorgeous color photographs—the very best images available. This second edition includes more than 500 new photos and updated text, maps, and species names. For most species, there are photographs of topsides and undersides, males and females, and variants. All text is embedded in the photographs, allowing swift access in the field, and arrows point to field marks, showing you exactly what to look for. Detailed, same-page range maps include information about the number of broods in each area and where strays have been recorded. Color text boxes highlight information about habitat, caterpillar food plants, abundance and flight period, and other interesting facts. Also included are a quick visual index and a caterpillar food plant index. The result is an ideal field guide that will enable you to identify almost every butterfly you see.