HETEROPTERA

G.G.E. Scudder

TRENDS IN SPECIES OCCURRENCE AND ABUNDANCE

There is little data to indicate any definite trends in species occurrence and abundance. Even the Douglas-fir cone seed bug (Leptoglossus occidentalis), which has shown definite increase in range and abundance in the Mixed-wood plains ecozone (Marshall 1991), does not show a clear increase in range in the Montane Cordillera, although it may have increased in the Vancouver area (Spencer 1945). However, the western boxelder bug (Leptocoris rubrolineata) may have increased its range (Spencer 1945).

There are however, a number of increasing threats to some species, in the form of habitat elimination. This is most evident in the South Okanagan Basin ecosection, wherein most of the 48 potentially rare and endangered species occur (Scudder 1994, 1996) (Table 3).

In contrast to the six endemic species of Heteroptera in the Montane Cordillera ecozone (Table 4) are reported mostly from forested sites. These sites are likewise not protected. Figure 10 shows that virtually all of these 48 species are confined to the Dry Interior of the ecozone, occurring only in the Bunchgrass, Ponderosa Pine and dry subzones of the Interior Douglas Fir biogeoclimatic zones. Very little of these low elevation ecosystems are protected, and they are in an ever increasing threat from development and urbanization. The Antelope-brush ecosystem, in which most of the rarest species occur, is rapidly being converted into vineyards or industrial sites, with resulting extreme habitat fragmentation and degradation. Because over the past century more than 60% of the Antelope-brush ecosystem has been destroyed (Schluter et al. 1995), leaving only about 9% of the ecosystem now relatively undisturbed (Redpeth 1990), the rare and other species contained therein are obviously in some danger. Some species of the rare Heteroptera are known from only one or two sites in the South Okanagan. However, protection of these irreplaceable sites is not guaranteed.

A few of the rare Heteroptera, such as the saldid Ioscytus politus, the mirids Trigonotylus antennatus and T. longipes, and the backswimmers Notonecta spinosa and N. unifasciata andersoni, are associated with alkaline lakes and alkaline lake margins. These habitats are also endangered in the South Okanagan Basin ecosection (Scudder 1993), wherein 85% of the riparian habitats have been destroyed.

It is obvious that future ecological monitoring and assessment should be concentrated in the Antelope-brush and riparian ecosystems in the South Okanagan. They could totally disappear in the next 20 years.