"SHORT-HORNED" BUGS
(HOMOPTERA: AUCHENORRHYNCHA)
K.G.A. Hamilton
FAUNAL CHANGES
Although historical data is scanty, the “short-horned” bug fauna of the MCE is obviously in transition. Some faunas have not been verified for years; others which represent presettlement ecosystems that once were widespread are now confined to highly localized patches; and a considerable influx of exotic species is documented here. These processes can only accelerate in the future unless major changes in land use, pollution and conservation practices are enforced.
The fragmented nature of the faunal associations makes them highly vulnerable to human activities, yet we know little about them. The insects endemic to Ecodistrict 1002 are some of the most isolated in the MCE. They are also the least studied. Colladonus aureolus (Van Duzee) and Oliarus beirnei Meade & Kramer have not been seen there since 1926, Oliarus coconinus Ball since 1933, Pissonotus rubrilatus Morgan and Beamer since 1938, while Okanagana ornata (Van Duzee) has not been collected in British Columbia since 1947. Additional work is needed in this part of the MCE to determine whether these populations persist to this day.
Almost 20% of the entire MCE fauna of “short-horned” bugs are limited to native vegetation in such limited valley systems. These are the very valleys most coveted by people, either for agriculture, housing or recreation. The human impact is felt further afield than directly transformed areas, as weed species and grazing effects spread out from fenced areas into surrounding woodlots, shrub semidesert and grasslands. Furthermore, the whole area around habitations of any size is experiencing alteration by the number of exotic insect species introduced by human activities. These aggressive and fecund bugs rapidly displace native faunas wherever European plants are found. They probably do not affect the fauna of larger native plants (trees and shrubs) or those that grow in extensive areas (dominant grasses). The faunas of herbs and rarer grasses are probably vulnerable to decimation.
Fully 25 species of introduced "short-horned" bugs are known from the MCE. All but five of these are foreign "exotics", representing 32% of the entire such fauna in Canada. Most are European; one is Asian, Japananus hyalinus (Osborn). Eleven attack ornamental trees and shrubs, eight feed on a wide variety of broad-leafed plants, five infest grasses and two are agricultural pests: Macropsis fuscula (Zetterstedt) and Typhlocyba prunicola Edwards, both on raspberry and related berries (Rubus spp.) Some of these, like the rose leafhopper Typhlocyba rosae (L.) or the meadow spittlebug, Philaenus spumarius (L.), were already widespread by the time intensive collecting began. The latter is a very invasive species that is probably the first European insect to have been introduced to North America, as the Newfoundland populations are probably of Viking origin (Hamilton 1979).
Introductions continue to occur and perhaps at an accelerating rate. Seven additional “exotics” were reported from the 21-year period between the world wars: Ceresa alta Walker in 1919, Aphrodes costatus (Panzer) in 1921, Rhytidodus decimaquartus (Schrank) in 1922, Ribautiana ulmi (L.) in 1924, Anoscopus serratulae (Fabricius) and Paramesus ?nervosa (Fallén) in 1926. Five were added in 21 years after the second world war: Macropsis fuscula (Zetterstedt) and Aphrodes bicinctus (Schrank) in 1950, Neophilaenus lineatus (L.) in 1953, Typhlocyba prunicola Edwards in 1953 and Fieberiella florii (Stål) in 1961. Compared to these, there were ten more in the next ten years: Japananus hyalinus (Osborn), Doratura stylata (Boheman), Macropsis graminea (Fabricius), Typhlocyba barbata Ribaut and T. lethierryi Edwards in 1970 and Opsius stactogalus Fieber in 1971, plus Idiocerus cognatus Fieber, Oncopsis tristis (Zetterstedt), Delphacodes propinqua (Fieber) and Liburniella ornata (Stål), all first discovered in 1976.
The rich Okanagan valley fauna is most strongly affected by such changes. All exotic species of bugs in the MCE are found in the Okanagan, while at the same time the native fauna is being decimated. Distinctive faunal and floral zones are disappearing due to irrigation and destruction. Housing and industrial development is rapidly overtaking whatever valley land is not already occupied by orchard and reserve. This loss of native valley habitats is catastrophic throughout most of the heavily settled areas, and herculean efforts such as trenching access roads sometimes seem warranted to protect the tiny fragments left.
Conversely, climate change could increase rather than decrease faunal richness in the MCE. The presence of great topographical differences in close association makes the fauna resilient in the face of climate change. Warming trends would only force populations to seek habitats at higher elevation in the immediate vicinity of their present range, and would not necessarily result in immediate faunal influxes to more northerly areas. However, some of the more mobile species would undoubtably be able to migrate further north and establish populations in valleys presently innocent of their presence. About 140 species are presently limited to southern valleys (the 1400 degree-day regions of the MCE) with many more in warmer areas of Washington and Idaho state. There is thus great potential for increased numbers of widespread species with only a slight increase in global temperatures.
