706 Invasive Stink Bugs and Related Species (Pentatomoidea)
traces left by mated females of Murgantia histrionica, compared with traces from virgin females, males,
or parous host females. However, the chemicals that mediate this interaction have not been identified,
and, in general, there is almost no information about the cuticular lipids of pentatomoids and their pos-
sible functions as intra- or interspecific semiochemicals.
15.4.2 Pentatomid Compounds as Kairomones for Diptera
The dipteran family Tachinidae has approximately 10,000 described species, and tachinid flies are the
largest and most important groups of parasitoids within the Diptera. All tachinids are endoparasitoids of
other arthropods, mainly insects (Aldrich et al. 2006, Nakamura et al. 2013). Chemically mediated inter-
actions between tachinids and their hosts have been studied in a number of systems (Feener and Brown
1997), including the exploitation of pentatomid pheromones as kairomones by tachinid flies (Mitchell
and Mau 1971; Harris and Todd 1980; Moriya and Shiga 1984; Aldrich et al. 1984, 1987, 2007; Aldrich
1995a,b; Mishiro and Ohira 2002; Adachi et al. 2007; Jang and Park 2010; Higaki and Adachi 2011). The
topic also has been reviewed recently (Nakamura et al. 2013).
Analogous to the platygastrid egg parasitoids, tachinid flies use multiple strategies to locate their hosts,
including exploitation of the pheromones of their prey. Similarly to Telenomus podisi, tachinid flies can
be attracted to the volatile pheromones of a variety of stink bug species, even though the molecular struc-
tures of the pheromones are dissimilar. For example, in field experiments, Euclytia flava (Townsend)
was caught in traps baited with several different pentatomid pheromones, including (E)-2-hexenal +
α-terpineol (Podisus maculiventris), methyl (2E,4Z,6Z)-2,4,6-decatrienoate (Thyanta spp.), and methyl
(2E,4E,6Z)-2,4,6-decatrienoate (Plautia stali) (Aldrich et al. 2007). The responses to different host
pheromones may be an adaptation to the different seasonal activity periods of its various hosts because
E. flava is seldom captured in traps baited with P. maculiventris pheromone in late summer or early fall
when P. maculiventris would not be producing pheromone, and this fly almost never emerges from over-
wintering P. maculiventris in the spring. Instead, during the later part of the growing season, E. flava
were collected primarily from Thyanta spp. hosts. Therefore, these tachinid flies may have adapted to
the different seasonal activity periods of their hosts, so that they can exploit a succession of host species
throughout the growing season (Aldrich et al. 2006).
Aldrich (1995b) reported that it is occasionally possible to find Podisus spp. nymphs parasitized by
tachinid flies in the field. Field experiments using reconstructed nymphal gland secretions containing
4-oxo-(E)-2-hexanal + linalool + tridecane supported this observation, with two species of tachinid flies,
Euclytia flava and Hemyda aurata (Robineau-Desvoid), being attracted to the lures (Aldrich 1988).
In general, there have been relatively few studies demonstrating attraction of tachinid flies to stink
bug secretions, in part because the parasitoids are laborious to rear. However, field observations have
shown that these flies generally parasitize adults of both sexes, rather than nymphs, suggesting that the
pheromones or other secretions of adults likely mediate these interactions. For example, a field experi-
ment using (E)-2-octenal, a common stink bug allomone, combined with the sex pheromones of Podisus
spp. and Euschistus spp., showed that attraction of the tachinids was not influenced by the presence of
(E)-2-octenal, suggesting that the pheromones were the more important part of the volatile cues used by
the flies to locate hosts (Aldrich and Zhang 2002).
Chloropid and milichiid flies also have been reported to be attracted to defensive compounds produced
by stink bugs. These small flies are scavengers, so they are probably attracted by the scent of injured or
dead bugs to feed on hemolymph, for example. Eisner et al. (1991) showed that milichiid flies (almost
exclusively females) from four genera (Paramyia, Neophylomyza, Milichiella, and Desmometopa) were
attracted to the stink bugs Piezodorus guildinii, Nezara viridula, and Euschistus sp. when these stink bugs
were being attacked by the spider Nephila clavipes (L.) (Araneae: Nephilidae), and also were attracted
to their common defensive compounds, (E)-2-hexenal and hexanal. Kondo et al. (2010) demonstrated the
rapid attraction (typically in about 2 seconds) of female Milichiella lacteipennis (Loew) to crushed adults
of Pentatomidae and Coreidae in Colombia, but did not test chemical attractants separately. Aldrich and
Barros (1995) showed the field attraction of female Milichiella arcuata (Loew) to (E)-2-hexenal, and the
attraction of chloropids (15 species total, predominantly females) to (E)-2-hexenal, (E)-2-octenal, and
(E)-2-decenal, common defensive compounds of pentatomids and coreids.