106 
Journal of Agricultural Research 
Vol. XXX, No. 2 
KEY TO SPECIES OP THE SOBGENUS OBTHEZIA » 
a. Ventral abdominal area, inclosed by ovisac band, without any transverse rows of spines; dorsal secretion 
confined to small tufts forming two complete, but narrow, longitudinal, submedian bands and 
exposing a wide expanse of bare derm between dorsal and marginal secretion of each side. 
...instants Douglas. 
oo. Ventral abdominal area with at least some spines in transverse ro ws, or, if without spines, with numer¬ 
ous small truncate conical tubercles in similar transverse rows, the dorsum in the latter case com¬ 
pletely covered by secretion and with complete spine bands. 
b. Dorsal spines confined to 5 small pairs of clusters along the median line on the posterior abdominal 
segments, secretion similarly limited, most of the dorsum completely exposed; marginal spine 
clusters and corresponding secretion obsolete anteriorly, ventral abdominal bands of spines poorly 
developed, each a single row of scattered spines..... nuda Ferris. 
bb. Dorsal spines, at the least, forming two complete median longitudinal rows as in insignis, usually 
forming more or less complete, wide, transverse bands; marginal spine cluster pairs complete, 11 in 
number; ventral abdominal bands of spines usually distinctly developed, and even broad; dorsal 
and marginal secretion corresponding to the spine arrangement. 
c. Transverse rows of spines in ventral abdominal area replaced by similar rows of small truncate 
conical tubercles, each heavily chitinized, but with nearly membranous cap; ovisac band with 
numerous disk pores through the outer fourth, but without these along or through the inner 
margin; dorsal spine bands and secretion very well developed; 7 pairs of abdominal spiracles.... 
..... mexicana, new species. 
cc. Transverse bands of spines in ventral abdominal area unmodified; ovisac band varying according 
to the species; dorsal spines and secretion varying. 
d. Some of the spines, in patches among the dorsal spine bands, conspicuously larger and more 
heavily chitinized than the average; dorsal spine bands and secretion complete; 8 pairs of 
abdominal spiracles and an anterior, median, elongate, dorsal chitinized derm patch. 
... caudata Ferris. 
dd. All dorsal and marginal cluster spines approximately uniform in size, shape, and chitinization; 
other characters varying. 
e. Spines making up spine collar surrounding opening of each thoracic spiracle very short conical, 
differing conspicuously in shape from remaining body spines; 8 pairs of abdominal spiracles; 
anal ring not sharply angulate within anteriorly and posteriorly, often with a distinctly 
developed chitinized wing on each side; inner spines of the 2 posterior dorsal clusters more or 
less distinctly reduced in size as compared with the remaining spines. 
/. Dorsal spine bands on thorax and anterior abdominal segments, while transverse, terminated ’ 
far from the corresponding marginal clusters, leaving a wide, bare, longitudinal derm band 
between dorsal and marginal spine clusters; secretion corresponding, leaving that portion of 
the derm exposed in perfect specimens; lateral wings of anal ring not developed or only 
slightly so; ovisac band inclosing only 3 transverse spine bands. nigroeincta Cockerell. 
ff. Dorsal spine bands continuous almost to corresponding marginal bands, although with the 
abdominal bands narrowed laterally, the dorsal surface, in perfect specimens, not, or only 
very slightly exposed; lateral wings of anal ring well developed, very evident; pore bands of 
anal ring incompletely developed; ovisac band inclosing 5 transverse bands of spines. 
g. Larval antennae 6-segmented; inner spines of the 2 clusters just before anal ring conspicu¬ 
ously smaller than the remainder in the larva. annae Cockerell. 
gj. Larval antennae 5-segmented, the third very long and more or less constricted medially; 
none of the spines in the clusters Just before anal ring conspicuously reduced in size in 
larva...... sonorensis Cockerell. * * * 4 
• The species americana (Walk.), arenariat Vays., and vatbuehii Kuw. have been omitted from this key, 
as no specimens of any of the three are available for comparative study. The status of americana will 
probably never be determined with certainty, but the other two species, from the descriptions, are evidently 
very closely related to urticae (L.). 
4 No clear-cut and distinct morphological differences that will definitely separate the adult females of 
these two species, annae and tonoreneie, have as yet been isolated; some comparative and apparent 
differences are indicated in the descriptions and figures of the two species. 
