488 Invasive Stink Bugs and Related Species (Pentatomoidea)
10.7.4 A Strong Pressure of Natural Enemies
If Antestia bug fecundity can be considered as relatively high, the same is not true for egg viability in
nature. In fact, as shown in Section 10.6.2.3 (Biological Control), egg parasitism, mainly due to platy-
gastrids, can reach rates as high as 95% in coffee plantations, with rates usually exceeding 50%. Antestia
bug nymphs and adults also are parasitized by Hymenoptera. Thus, the growing capacity of Antestia bug
populations may be slowed by strong pressure from parasitoids.
Moreover, most of the parasitoid species listed in Section 10.6.2.3 have been collected from differ-
ent species and subspecies of Antestia bugs over wide geographical areas from Western to Eastern and
Southern African coffee-producing countries. This suggests that these parasitoids are adapted to a wide
range of habitats, at least wider than that of their hosts. Moreover, this suggests that most of these parasit-
oids may be opportunistic rather than specific to Antestia bugs and may not depend on these bugs alone
to develop. Therefore, egg parasitoid ubiquity and density in coffee plantations may play a crucial role in
the limitation of Antestia bug expansion to new areas.
10.7.5 Constraining Ecological Preferences
The distribution of Antestia bug species over Africa as well as the biological data reported in the litera-
ture suggest that expansion of these pests is limited by constraining ecological preferences, which differ
from one species to another. Antestiopsis thunbergii, including its subspecies and different geographic
forms, is more adapted to climatic conditions of Eastern and Southern African highlands. The optimal
temperature for A. thunbergii bechuana was found to be 23°C in a recent study (Ahmed et al. 2016).
The other species of major economic importance, A. intricata, is present on coffee in West and Central
African highlands, from the Atlantic Ocean to Uganda and Ethiopia, and seems to be adapted to a wider
range of temperatures because it has been found at low elevations on Robusta coffee. The overlapping
area of these two species is limited to Ethiopia and the countries of the Great Lakes region (Uganda,
Rwanda, and Burundi), where both A. thunbergii ghesquierei and A. intricata are present on Arabica
coffee. This region is considered to be a transition zone between different biogeographical regions in
Africa (Linder et al. 2012), and the different Antestia bug species apparently find here suitable liv-
ing conditions. However, globally, Antestia bugs are distributed according to the main biogeographical
regions of Africa, as considered by Linder et al. (2012). For example, A. thunbergii mainly occurs in the
Somalian, Zambezian and South African biogeographical regions, whereas A. intricata mainly occurs in
the Guinean and Congolian biogeographical regions. Clearly, Antestia bug species have not expanded to
all Arabica coffee-growing areas of Africa, showing that they have constraining ecological preferences.
10.7.6 A Close Relationship with Host Plants of the Family Rubiaceae
Antestia bugs have been found on a large range of host plants (Section 10.3.2, Feeding Habits). However,
coffee and related species of the Rubiaceae are the main host plants of the group (Hargreaves 1936, Le
Pelley 1942). Some of the wild plants in this family are present in close proximity to coffee plantations.
These alternative host plants may play a role in the Antestia life cycle and in the coffee colonization
process in such a manner that their presence is crucial for optimal development of Antestia populations.
Thus, this close relationship with the Rubiaceae may limit the expansion of Antestia bugs on coffee
where these alternative host plants are absent.
10.8 Acknowledgments
The authors thank the following individuals for providing information referenced in this chapter.
We wish to thank Teresiah N. Njihia (Plant Health Department, International Centre of Insect Physiology
and Ecology, Nairobi, Kenya) and Sylver Habumugisha (School of Agriculture, Rural Development and
Agricultural Economic, University of Rwanda, Butare) for allowing their unpublished data to be cited. We
also are grateful to the late Jacques Carayon (Entomologie Agricole et Tropicale, Museum National d’Histoire