June, 1918 Bulletin of the Brooklyn Entomological Society ol 
designations cerci and styli (“c” and “s” of all figures) need no 
explanation. I have used the term phallus for the true penis “ pe” 
of the different figures, since the designation “penis” has been 
applied to all manner of structures, such as the accessory organs 
at the base of the abdomen in male Odonata, etc., and it would 
create confusion to apply the term penis to the phallus in such 
cases. The fitillator is the structure labeled “ep” immediately 
above the phallus, and is sometimes referred to as the epiphallus. 
The phallus is an extremely variable structure even within the 
same group of insects, and the difference between the phallus of 
certain species of the same genus of Diptera, for example, is so 
great that it is almost impossible to homologize the parts, so that 
in many instances, it is advisable to make merely a tentative 
homologization of the various portions of the phallus, leaving the 
definite determination of the parts until more intermediate forms 
are available for comparison. 
In certain Apterygota such as the Sminthurids (Fig. 88) and 
the Japygids (Fig. 87) the phallus “p” is little more than a 
pappilla, presenting no features of especial interest for a study of 
the parts in winged insects. In the Protura (Fig. 86), on the 
other hand, the phallus is bipartite, that portion here figured being 
composed of a pair of median structures “eu” through which the 
ejaculatory ducts empty, and a pair of so-called parameres “ pr.” 
Traces of such a bipartite phallus are retained in the partially 
divided organ “pe” of the Lepismoid insect Nicoletia (Fig. 95), 
while in the Lepismid shown in Fig. 94, the two parts of the 
phallus “pe” are quite closely united. For the sake of brevity, I 
would use the designation “diphallic” to refer to the type of 
phallus made up of two parts, and “ monophallic” to refer to the 
forms in which the parts of the phallus have united to form a 
single organ, or in which one of the halves of the phallus has 
been lost. 
Among the Pterygotan insects, the Ephemerids (Figs. 4, 5, 9, 
and 15) have retained the diphallic condition in most instances. 
Some Plecoptera (Fig. 16, “pe” ) have retained the diphallic con- 
dition, but most of the specimens studied were monophallic (Figs. 
iw U7 ete pen). lhe money primitive, Dermuaptera isucky as 
Echinosoma (Fig. 24, “pe’’) are diphallic, while the higher ear- 
