/ 
The First Abdominal Segment of Embryo Insects. 99 
Zaitlia fluminea, Say. * 
[Plate 3 Figs. 17 and 18.] 
Of this form I have examined only embryos in the stages immediately 
preceding, during, and after revolution. Just before revolution the embryo 
lies on one face of the yolk with its amnion and serosa in contact and not 
separated by a layer of the vitellus as in most of the Hemiptera whose on¬ 
togenies have been studied. Hence Zaitlia would seem to resemble the 
Orthoptera and Coleoptera in its manner of embryo formation. The stages 
which I have studied show only the fully developed pleuropodia; I can, 
therefore, assert nothing in regard to the process whereby these organs 
originate and disappear, although their resemblance when fully formed to 
the pleuropodia of Cicada renders it highly probable that the beginning 
and end of their development are no less similar to those observed in the 
Homopteron. 
In Fig. 17 I have represented half a cross-section through the first 
abdominable segment of an embryo during revolution. The ectoderm 
[eccZ] of the dorsal surface in the neighborhood of the heart [c6] is much 
thinner than the ectoderm laterad to the large ganglion [pZ]. In one place 
near the large pleural fold filled with adipose cells [acZJ the ectoderm is 
greatly thickened to form a bulbous organ which is to be regarded as a 
pleuropodium. The cells composing it are greatly elongated, being 
three or four times as long as the thickest ectoderm cells of the ventral 
body wall. It is also seen that a great number of cells take part in the 
formation of the Zaitlia pleuropodium while but very few go to make up the 
same organ in Cicada. In the water-bug the rounded inner face of 
the pleuropodium projects as far as the yolk and presents at irregular in¬ 
tervals a few flattened mesodermic elements [cn]. The inner ends of the 
long cells are coarsely granular, their outer ends uniformly hyaline. 
Their nuclei are but little larger than the nuclei of the body walls. The 
delicate hyaline cell-tips converge to form a flat surface which is covered 
* The eggs of this species were given me by Dr. W. Patten as the eggs of an aquatic 
Hemipteron, which from his description I took to be a Nepa, and mentioned it as such in 
my preliminary notes (’89a’89&). The species, however, can be no other than our com¬ 
mon Zaitha fluminea , Say, for I now remember Dr. Patten telling me that he found the 
eggs attached to the hemielytra of the female. This habit, according to Uhler (article 
Hemiptera , Standard Natural History Vol. II, p 258, 1884) is shared, so far as their habits 
have been observed, by all the species of this exclusively American genus. The female 
Nepa attaches her eggs to aquatic plants. The chorion of the egg is smooth and unorna¬ 
mented in Zaitha , while the egg of Nepa has at one end seven hair-like radiating pro¬ 
cesses, which, according to E. v. Ferrari , make the egg resemble the seed of Carduus 
benedictus. (Die Hemiptcren-Gattung Nepa , Latr (sens, natur.) Annalen d. K. K. naturhist. 
Hofmuseums. Bd. Ill, No. 2. Wien 1888.) 
I hasten to correct my mistake, as the species of Nepa and Zaitha are not only gener- 
ically distinct, but belong to different families: the former to the Nepidoe , the latter to the 
Belostomatidce. 
