FAMILIES OF THYSANOPTERA OF BRITISH COLUMBIA
R. A. Cannings and G. G. E. Scudder
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Key to Families of Thysanoptera
1. Last abdominal segment broadly rounded or conical (Fig. 18.1); female usually with ovipositor; forewings (if present) with 1 or 2 longitudinal veins, and surface with microscopic setae (Fig. 18.3) (Terebrantia) .........................2
- Last abdominal segment tubular (Fig. 18.2); female without ovipositor; forewings (if present) either without veins, or with a short median vein not extending to tip, surface smooth and without microscopic setae (Fig. 18.4) (Tubulifera) ...........................................................................................Phlaeothripidae
2. Female with ovipositor turned upwards (Fig. 18.5); antennae 9 segmented, segment III usually with senoria either elongate and linear or transversely linear (Fig. 18.7, 18.8, 18.9); forewings broad with several cross veins ............................................................................................Aeolothripidae
- Female with ovipositor turned downward (Fig. 18.6); antennae usually with 7 or 8 (rarely 6 or 9) segments (Fig. 18.10); senoria on segments III and IV developed into slender, single (Fig. 18.11) or forked sense cones (Fig. 18.12); forewings narrow, with one cross-vein
Description of Families
These primitive thrips can be distinguished from other thrips in British Columbia by having relatively broad wings, with rounded tips (when present), elongate oval or longitudinal sensoria on the third and fourth antennal segments. The maxillary palps are three-segmented, and the labial palps are four-segmented. The female has an ovipositor that is curved upwards. Like the Heterothripidae, the Aeolothripidae have cocoon-breaking hooks on the base of the fore tarsi.
Worldwide there are about 250 species in this family contained in about 27 genera. In Canada, 18 species in three genera are recorded. In British Columbia, seven species are reported in the genera Aeolothrips Haliday (5 species) and Orothrips Moulton (2 species).
The genus Aeolothrips occurs mostly in the Northern Hemisphere. Most live in flowers where they are facultative predators, feeding on small arthropods and pollen. However, a few species live on the leaves of trees, or at the base of grass tufts: both of these types are obligate predators, feeding mainly on mites. The most widespread species in British Columbia is Aeolothrips fasciatus (Linnaeus). It has been recorded from the B.C. interior, lower mainland and southern Vancouver Island. It occurs on Taraxacum officinale, Trifolium repens, Lotus corniculatus, Elymus sp., Prunus sp. and Solidego sp., as well as many other plants.
Species in this family have usually eight-segmented (rarely four- to seven-segmented) antennae with sensory cones on the third to seventh segments. The fore tarsi are one-segmented and unarmed basally, but can have teeth near the apex. The middle and hind tarsi are one- or two-segmented. The last abdominal segment is tubular, with the setae at the posterior margin of the tube seldom longer than the tube. The life cycle includes three pupal instars that can be found together with adults and larvae on plants.
Worldwide, about 3000 described species are now placed in this family, but many new ones remain to be described. In Canada, 56 species in 18 genera are recorded, with ten of these species in eight genera reported from British Columbia.
The biology and life cycle of the red clover thrips Haplothrips niger (Osborn) have been described by Loan and Holdaway (1955). This species occurs throughout southern B.C. being recorded from red clover, Chrysanthemum leucanthemum, rose, yarrow and apple.
Haplothrips leucanthemum (Schrank) which is recorded from Victoria, is an introduced European species, reported elsewhere from daisy and yarrow. Only parthenogenetic females of this species occur in Canada.
Members of this family have six- to eight- or sometimes nine-segmented antennae. These antennae have projecting simple or forked sensory cones on the third and fourth segments. The wings are narrow, with pointed apices covered with microtrichia, and the fore tarsi are unarmed. Females have a well developed, downward curved ovipositor.
The larvae in this family are usually phytophagous, occurring on mostly grasses and flowers. Many species are known to be pests in horticulture and agriculture.
Worldwide, there are about 1700 species in 260 genera reported, but many more remain to be described. In Canada, 87 species in 33 genera are recorded (Chaisson 1985). So far 28 species in 15 genera are known from British Columbia. Most belong to the genera Frankliniella Karny or Thrips Linnaeus.
Best known is the western flower thrips Frankliniella occidentalis (Pergander). This is an important vector of the tomato spotted wilt virus, and occurs as a pest in many parts of the world. It has been reported from both the B.C. interior and the lower mainland. It occurs on a large number of plants, both wild and cultivated. Hosts include broad beans, alfalfa, apple, and roses. It frequently causes serious losses to flower crops through its direct feeding damage, particularly on red flowers on which the white feeding scars are particularly obvious (Mound and Kibby 1998).
The onion thrips Thrips tabaci Lindeman, which is also widespread in British Columbia, likewise occurs on a wide variety of plants, including onions, loganberry, squash, potato, and ragweed. It is reported from houseplants and English cucumbers in greenhouses. The species is particularly broad in its feeding habits, being known to feed on mite eggs, as well as pollen and leaf tissue (Mound and Kibby 1998). It is a vector of tospoviruses.