Semiochemistry of Pentatomoidea 679
In spite of the fascinating complexity of interactions involving semiochemicals, historically, many
investigations into presumed stink bug semiochemicals have failed to adequately demonstrate the pur-
ported functions of the various compounds. Instead, differences in the volatiles or gland contents pro-
duced by adult males and females have been used to propose functions for chemicals that are exclusive to
or much more abundant in one sex. However, until rigorous and meaningful bioassays demonstrating the
behavioral responses of conspecifics to specific compounds have been carried out, designation as phero-
mone components is not justified (Millar 2005). The same caveat applies to other classes of semiochemi-
cals: chemistry and biology must be investigated in tandem to establish whether a given substance, or
component of a multi-component emission, is indeed a semiochemical that elicits a behavioral response.
15.1.3 Justification for Research on Stink Bug Semiochemistry
Pentatomoidea are important in virtually all ecosystems of the world, and, as with other superfamilies
of true bugs, many are herbivorous. Other species are predators of other insects as well as feeding on
plants at least occasionally. Many stink bugs are pests whose importance has increased in recent years
because of the replacement of broad-spectrum insecticides with more selective suppression tactics for
control of other key pests, such as the deployment of transgenic crops that express insecticidal proteins,
use of mating disruption and insect growth regulators in control of tree fruit pests, and Lepidoptera- and
Homoptera-selective control tactics used in vegetable crops (Millar et al. 2010). All species of stink bugs
for which pheromones have been identified have male-produced pheromones that attract females and, in
many cases, also males and nymphs. These pheromones can potentially be exploited for monitoring and
possibly in attract-and-kill or other tactics for control of pest populations.
Identification of active pheromone components must be performed rigorously so as to ascertain: (1) the
minimum blend of compounds that are both necessary and sufficient to elicit activity equivalent to that
elicited by pheromones released by live bugs (Millar 2014), and (2) the ratio and release rate of compo-
nents that are optimally attractive under field conditions. It also is important to determine the functional
roles of other components that are present in crude extracts, particularly compounds that might inhibit
attraction of the species under study, or of congeners (i.e., to prevent cross-attraction between related
species). Thus, a methodical and thorough approach to the identification of semiochemicals is required
in order to exploit their full utility for integrated pest management (Millar 2014).
15.2 Pheromones: Overview and Species Accounts
Pheromones have been identified for approximately 45 species of Pentatomoidea, in 25 genera, all but
two of them in the Pentatomidae, as shown in Table 15.1). Approximately half of these have been dis-
covered since the thorough review of Millar (2005), and this chapter will focus primarily on advances
made since the publication of that review. This review covers the literature up until October 2015, when
the manuscript was submitted.
Almost all of the pheromones described to date are produced by adult male bugs. The exceptions
are the aggregation pheromones identified from nymphal pentatomids of a few species (Fucarino et al.
2004) and the so-called solicitation pheromones produced by cydnid nymphs (see below). The pattern
of responses elicited by the male-produced pheromones is divided roughly equally between those that
appear to attract only females, and those that attract both sexes, as well as nymphs when this has been
tested. Even this distinction may be variable: for example, the male-produced pheromone of Piezodorus
hybneri attracts approximately 90% females during the summer, but equal proportions of males and
females in the fall (Endo et al. 2010).
Below, we provide case studies of new discoveries since Millar’s (2005) comprehensive review, some
of which were also reported in Moraes et al. (2008b) for neotropical species. The chemistry is diverse
and challenging from the standpoint of stereochemical specificity, frequently involving molecules such
as sesquiterpenoids with multiple chiral centers. In spite of the analytical and synthetic chemistry chal-
lenges embodied in the often complex structures of pentatomid pheromones, many species will respond