163 
in the strongly marked venation of Sehirus (Fig. 6), Brochymena, and 
Tessaratoma, I believe to be the middle part of radius as in Homaemus, 
and the stem to be that of media and not radius. It remains to account 
for the vein extending basad along the first furrow from the apical part 
of media. It seems explainable only as a false vein, developed to 
strengthen the wing, analogous to the veinlike extension of the angula- 
tion of media in Sarcophaga. 
In the Pentatominae (Pl. XVI, Fig. 9), Asopinae (Fig. 4), Grapho- 
somatinae, and some Tessaratominae (Piezosternum) the stem of media 
seems to be complete from base to its union with the radial sector, closely 
contiguous to subcosta throughout, without trace of any hamus. Without 
the series at hand showing the gradual substitution of the medial stem in 
place of that of radius, this vein would be accepted without question as 
radius, and a divergence in evolution would consequently be assumed; on 
the one hand radius dominant, on the other, media. The two veins in 
the middle lobe converge strongly at base and meet in a curve. 
An interesting structure in Corimelaena (Thyreocorinae) is a strongly 
chitinized sub-basal portion of the first anal vein. This portion is turned 
slightly so as to be nearly parallel to the long axis of the wing, and has a 
fine and beautifully regular cross-striation. It is evidently a stridulatory 
organ. 
THE NYMPHS 
The genera are usually easily recognizable among nymphs; but in 
some genera at least the separation of species is more difficult than with 
the adults. The notal color-pattern is useful, for although it is quite 
variable in extent and shade the fundamental plan does not change. The 
identity of a species is, of course, best determined by rearing, but can 
often be safely deduced by careful comparison with the adult, with 
especial regard to the head and anterior region. The spines and angles 
of the adult are seldom similarly present in the nymphs; the wings and 
scutellar structures are undeveloped; but the tergum, of which we see too 
little in the adult, is revealed with its important and interesting structures. 
The pleural osteoles of the adult are wanting in the nymph, their function 
being performed by the tergal scent-glands. The abdominal margin bears 
on each segment a circular or elliptical differentiated thicker area, lapped 
over the edge, half of it above and half below. These I call simply 
lateral plates, usually referring to the dorsal part. Along the middle of 
the abdomen above and below are similar areas, the median plates, the 
dorsal ones containing the scent-glands. All these plates are variable in 
color, but constant in extent in each stage, being proportionately larger 
in the very young nymphs. 
The first scent-gland is on the hind margin of the third dorsal seg- 
ment. It is unlike the others *, more simple, and for aught I] know may 
not usually be functional. There is a long transverse “slit,” or impressed 
suture, derived from’the suture between the third and fourth segments, 
*In an undetermined pentatomid nymph from Manila this difference is remark- 
ably slight. 
