LUCY WRIGHT SMITH 
441 
Morphological Notes 
Adults. The interest which centered about the biology of 
Pteronarcys was aroused by the discovery of tracheal gills in the 
adult. Newport first described them in 1844. His paper contains 
a detailed discussion of their position and structure. Seven years 
later he published again on the anatomy of Pteronarcys. The 
article contains a more complete discussion of the gills, notes on 
the circulation of the blood, an account of the spiracles and the 
distribution of the trachea, and descriptions of the digestive, 
nervous and reproductive systems. A summary of his work is 
expressed in the following quotation: 
‘^Pteronarcys retains the larva type of organization in all its 
structures, branchial organs of respiration, a capacious eosopha- 
gus and elongated alimentary canal, and more numerous and 
separated ganglia in its nerve cord.” 
Hagen added to, and in part corrected, Newport’s work on 
the structure of the respiratory and reproductive systems. 
Packard has contributed a paper on the sclerites of Pt. cali- 
f arnica. 
The most interesting morphological asjiect of the genus 
Pteronarcys is found in the structure of the male genitalia. Any 
one who is familiar with Plecoptera knows what diversity of 
form the genital armature of the male presents; many groups 
are so highly specialized that several segments are modified in 
the formation of the copulatory organs, while in others there are 
no accessory appendages. Pteronarcys falls into the highly 
specialized group. 
The remarkable modifications in Pt. dorsata (regalis) attracted 
Hagen’s attention and in his paper on the mating habits of that 
species he discusses the structure in some detail. His manuscript 
contains further notes and sketches which Dr. Needham has 
copied and appended with comments of his own. The following 
description is drawn from both sources. It is the supra-anal 
plate which is of special interest. Here, in Pt. dorsata it is in the 
form of a sperm-conveyer. It is a median dorsal appendage 
(text-fig. B) entirely separated from the openings of the sperm 
ducts on the ninth segment by the anus which occurs on the 
eleventh. It consists essentially of three parts; an inner part 
(text-fig. B, I) which is buried in the musculature of the tip of 
TRANS. AM. ENT. SOC., XLIII. 
