50 Bulletin of the Brooklyn Entomological Society Vol. XIII 
edging my indebtedness and expressing my very deep gratitude 
to Mr. A. N. Caudell for specimens, identifications and literature 
in Orthoptera; to Dr. P. P. Calvert, and Mr. E. B. Williamson 
for material, identifications, and literature in Odonata; to Dr. L. 
O. Howard, Dr. A. D. Imms, and Mr. R. May for Embid ma- 
terial; to Dr. W. M. Wheeler and Mr. Ferris for Isoptera and a 
male of Timema; to Mr. C. C. Gowdey and Dr. K. Jordan for 
Dermapteron material; to Mr. Graveley for specimens of Humber- 
tiella; to Prof. R. A. Cooley for specimens of Peranabrus; to Dr. 
N. Banks for literature from his private library; and to Mr. J. A. 
G. Rehn, Dr. A. Morgan and Dr. N. Banks for identifications of 
Blattids, Ephemerids and Plecoptera. 
Those terminal abdominal structures which, from their wide- 
spread occurrence throughout the groups of insects here discussed, 
have proved to be of the most importance for a phylogenetic study 
are the pygidium or epiproct, the paraproct, the cerci, the phallus 
with the titillator, and the hypandrium with the styli. The term 
pygidium or epiproct refers to the tergal region of the eleventh ab- 
dominal segment or its homolog labeled “sa” in the various 
figures, and is a synonym of the designations supraanal plate, 
suranale, and median inferior appendage (of Anisoptera). The 
term paraproct refers to the regions homologous with the lateral 
portions of the eleventh abdominal segment, labeled “pa” in the 
various figures, and is a synonym of the terms parapodial plate, 
subanal plate, subcercus and the paired inferior appendages (of 
Zygoptera). The terms epiproct and paraproct (1. e., epiproctus 
and paraproctus) have been used in place of the more cumbersome 
English designations supraanal plate and parapodial plate, for the 
sake of brevity, and at the same time to emphasize their position 
with regard to the anal opening, which is one of the landmarks 
used in identifying these structures in the different groups of in- 
sects. The term hypandrium or hypoproct refers to the ventra! 
portion of the tenth abdominal segment or its homolog labeled 
“hy” in the different figures. This structure is also designated 
as the subanal plate, lamina subgenitalis or subgenital plate; but 
the true subgenital plate, or subgenitale, is the ventral portion of 
the eighth abdominal segment of female insects, and is therefore 
somewhat different from the hypandrium of the males. The 
