138 Invasive Stink Bugs and Related Species (Pentatomoidea)
well beyond the apex of the head. The bucculae are small, somewhat flap-like. The clavi usually meet
beyond the apex of the scutellum in a single point, sometimes forming a short claval commissure. The
scutellum is triangular, the apex is acute; the frena extend the entire length, from base to apex, of the scu-
tellum. The middle and hind coxae are widely separated; the tarsi are three-segmented. The abdominal
trichobothria are paired on each side of abdominal segments III through VII and transversely oriented.
In females, the second valvifers are fused, forming an M-shaped or W-shaped sclerite; the female sper-
mathecal duct lacks a dilation or sclerotized rod. Kumar (1971) provided a detailed study of urostylidid
genitalia and the alimentary canal. Five species of Urostylididae have been karyotyped, of which two
and three species had a diploid number of 12 + XY and 14 + XY, respectively (Ueshima 1979, Kerzhner
et al. 2004, Rebagliati et al. 2005).
The taxonomic history of this family has been even more confused than other pentatomoid fami-
lies. Through time, they have been associated with a number of different families, some pentato-
moid, some not. For example, Singh-Pruthi (1925) related them to the Acanthosomatidae, Yang
(1938, 1939) and Pendergrast (1957) to the Pyrrhocoridae, and Miyamoto (1961) to the Pentatomidae.
Most workers have, however, held the common belief that the urostylidids represent a basal position
in the evolution of the pentatomoids; in fact, China and Slater (1956) considered them to represent a
proto-Trichophoran group basal to the Pentatomidae, Coreidae, and Lygaeidae. The study by Grazia
et al. (2008) supports a basal position, placing the urostylidids as the sister group to the rest of the
Pentatomoidea.
There are no recent generic revisions available for this family, but several more comprehensive studies
have been published for certain geographical areas. For example, Yang (1939), Hsiao et al. (1977), and
Ren (1999) reviewed the Chinese urostylidids; Ren and Lin (2003) studied those species occurring in
Taiwan; and Ahmad et al. (1992) treated the taxa from the Indian subcontinent.
The family Urostylididae is one of three heteropteran families in which females are known to form
an ootheca, a structure protecting the mass/batch of eggs. Early works on the subject were in Japanese
(Yamada 1914, 1915). Kobayashi (1965) and later Kobayashi and Tachikawa (2004) described the
occurrence of ootheca as a gelatinous substance covering the eggs completely except for the apices
of the micropylar processes. They studied four species from two genera: Urostylis westwoodii Scott,
U. striicornis Scott, Urochela luteovaria Distant, and U. quadrinotata (Reuter). The egg batch usually
is deposited either on the bark or in a crevice of the bark and is covered by a substance of a different
color, often transparent or glossy. An interesting account of this behavior was provided by Kaiwa et al.
(2014); they studied the life cycle of two species in Japan. The females have enlarged ovaries that produce
a polysacharide (jelly-like) excretion. Endosymbionts from specific organs in the genital chamber are
passed into the jelly during oviposition (vertical symbiont transmission). Eggs are laid in November, and
nymphs hatch in February (end of winter, which is exceptional within the Heteroptera) before plant hosts
(Quercus spp.) have formed leaves. Nymphal instars I through III remain on the egg mass, feeding on the
jelly containing the symbiotic bacteria.
Additional biological information is meager. Urostylidids have been recorded from a variety of plants,
but there seems to be preference for various tree species (Cornaceae, Fagaceae, Pinaceae, Rosaceae,
Theaceae, and Tiliaceae). They occasionally have been considered pests.
2.3 Conclusions
We now have presented taxonomic histories, synopses, and various comments on all of the pentatomoid
families and on the pentatomid subfamilies, tribes, and species groups known to us. We hope this estab-
lishes a foundation upon which new phylogenetic work can be built. In our opinion, the main barriers
that must be overcome in developing such a classification include, but are not limited to (1) the size of
the project (over 50 tribes and generic groups within the Pentatomidae alone); (2) the interpretation of
morphological characters; and (3) the lack of specimens for molecular research.