|scientific name Sitona lineellus |
common name Alfalfa Curculio
Agricultural systems where clover, alfalfa, vetch and sweet clover are found (Campbell et al. 1989).
Peak periods of activity occur between April and June (Campbell et al. 1989).
Body length varies from 2.9 to 4.0 mm, excluding head. Integument is generally black with an occasional reddish tinge; tarsi, tibia, femora, and antennae are reddish. The rostrum surface is flat but may be weakly covex on the upper two thirds. The lower third of the rostrum may be weakly concave and the medial carnia is absent. Eyes are strongly covex and protuberant. The length of the pronotum equals the width. The pronotum is widest at the middle, the sides are weakly arcuate and the anterior constriction line is weakly evident. The pronotal surface is covered with deep and close punctures that possess forward pointing, slightly erect scales, giving the surface a shiny appearance. The prosternal groove is approximately equidistant from the fore-coxae and the anterior of the prosternum. Elytral sides are subparallel on the basal half, and the remainder is broadly rounded. Strial punctures are small, weakly impressed and each possesses a small recumbent seta. The vestiture is variable, but generally consists of dense, small, recumbent interstrial scales, that are white or brown. Females are similar to males, but the elytra are more inflated, lateral margins of elytra are more arcuate, the body is larger, and females have a more diffuse colour pattern. Adults are most easily recognized by: a) strongly convex eyes; b) narrow pronotum; c) small body size compared to other Sitona species; and d) median row of narrow and erect scales, coloured white in each elytral interstriae. (Adapted from Bright 1994, Bright and Bouchard 2008)
Sitona lineellus is a univoltine species, undergoing one generation per year, and the adults are long lived, with the life span reaching up to eleven months, approximately five months of which are spent in overwintering habitats (Campbell et al. 1989). Adults overwinter on the soil beneath thick layers of organic debris (Loan 1963) and become active as early as mid-April (Campbell et al. 1989). Overwintered adults are wingless; hence, migration in the spring is achieved via walking to find hosts in adjacent fields (Campbell et al. 1989, Anderson 1997). Once emerged in the spring, mating and feeding begin. Newly emerged adults are sexually mature by autumn of the previous year and mating does occur before the overwintering months, however, very few females oviposit in the autumn (Campbell et al. 1989). Once mated in the spring, eggs are scattered over the soil surface between April and June (Loan 1963, Anderson 1997). A single female will oviposit between 110 and 180 eggs, laying an average of eight to 12 eggs per day (Campbell et al. 1989). The time required for incubation varies with temperature and moisture levels. Four larval instars occur in the soil; the early instars feed within root nodules and the late instars are more mobile in the soil and consume both roots and root nodules (Loan 1963). Pupae may be found in the soil as early as late June, and new generation adults may be found as early as the first week of July (Loan 1963). The period between oviposition and new generation emergence is about nine weeks (Loan 1963). Feeding by the new generation begins immediately after emergence, but is not believed to continue as long as the late season feeding of other Sitona species (Loan 1963).
Populations rarely reach outbreak levels in North America, but are commonly found (Campbell et al. 1989).
Larval feeding occurs within the root nodules of Vicia cracca L. (vetch) and Medicago sativa (alfalfa) (Loan 1963). Adults consume vetch and alfalfa foliage, as well as the foliage of red clover, alsike clover, peas, sweet clover, pea flower (Caragana arborescens) and garden flowers including tulips and delphinium.
This species has been reported from a number of sites across Canada, in all provinces and territories, both in northern and southern regions (Campbell et al. 1989, Bright and Bouchard 2008). It also occurs in Alaska, most of the United States, Europe and Asia (Bright and Bouchard 2008).
Sitona scissifrons Say, a species believed to have been North American, has been established by Bright (1991, 1994) as a synonym of Sitona lineellus. Furthermore, North American specimens identified as Sitona tibialis Herbst, a European species, are in fact S. lineellus, and Sitona tibialis is, at this time believed to have only occurred in North America near Chicago, Illinois, likely as a result of a limited introduction due to imports received from Europe at this location. Research regarding this species in North America as a result, may appear under any of these three species names. Sitona lineellus is believed to be an introduced species, originating from Europe and first found in Ontario (Campbell et al. 1989). However, as this species is widespread throughout the Yukon Territory and most Canadian provinces, Anderson (1997) suggests that it is likely a native species.
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