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Euaresta stelligera (Coquillett)

Recognition
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Euaresta stelligera is one of the species of Euaresta with the anterior notopleural seta present, the apex of cell r₂₊₃ with 2 marginal hyaline spots, and the ground color of the thorax dark brown.. In wing pattern it closely resembles E. bella, E. stigmatica, and especially E. bellula, in that the bulla is always present and the basal half to two-thirds of cell r₄₊₅ is dark. It and E. bellula usually have two marginal hyaline spots present in cell r₁; if a third, apical one is present, it is small and does not cross vein R₂₊₃. The basal marginal spot broadly crosses this vein. In E. bella and stigmatica, the basal marginal spot in cell r₁ is always interrupted at the vein, whereas the subapical spot crosses it broadly. Euaresta stelligera can be further distinguished from E. stigmatica by its pterostigma never having more than a basal hyaline spot, and from E. bella by its mostly nonmicrotrichose abdominal tergite 5 (Foote et al. 1993). Euaresta stelligera is extremely similar to E. bellula, but differs in almost always having shiny, lateral nonmicrotrichose areas on abdominal tergite 4 and often tergite 3 and syntergite 1+2, a slightly broader gena (height 0.075-0.14 mm., more than two-thirds width of first flagellomere vs. 0.04-0.08 mm., less than two-thirds width of first flagellomere in E. bellula; see Table 1), femora often with brown spot, streak or larger area (vs. always entirely yellow in E. bellula), and a usually slightly more rapidly tapered aculeus tip.

Classification and Evolutionary Relationships
Order: Diptera. Family: Tephritidae. Subfamily: Tephritinae. Genus: Euaresta. Species: stelligera. Author: Coquillett.
Relationships among the species of Euaresta were analyzed by Norrbom (1993). Click here for more detailed discussion of Euaresta phylogeny. Euaresta stelligera has been placed in the bullans species group.

Names Used for this Species
Trypeta (Euaresta) stelligera Coquillett 1894: 74.
Trypeta stelligera: Aldrich 1905: 605.
Euaresta stelligera: Berlocher 1984b: 354.
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Type Data
Holotype - Male (USNM), USA: southern California [Los Angeles Co.].

Distribution
Euaresta stelligera is known from coastal areas of Canada (British Columbia, north to Queen Charlotte Is.), USA (Washington, Oregon, California), and northern Mexico (northern Baja California Norte). Three specimens from Colorado (Jefferson County, Red Rocks Park, near Morrison, 6 Mar 1985, J. A. Powell, UCB USNM00054989-91) are the only known specimens from a locality significantly far from the coast. If not mislabeled, these specimens represent an interesting Euaresta population.
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Biology
Ambrosia chamissonis (Lessing) Greene is very probably a host plant of Euaresta stelligera. Adult flies have been collected from this plant on on numerous occasions (Berlocher 1984;  see also Specimen data), and the ranges of these fly and plant species are similar (coastal British Columbia to Baja California). The rearing record from male flowers reported by Goeden & Ricker (1974) probably pertains to E. stelligera; although unfortunately no reared voucher specimens have been preserved (R. D. Goeden, pers. comm.), the preserved adults collected by Goeden & Ricker from this plant are all E. stelligera.

Foote & Blanc (1963) reported specimens as E. bellula "ex" A. acanthicarpa Hooker based on a series of E. stelligera collected from Del Monte, California, by H. H. Severin. It is likely that these specimens were swept rather than reared, and the status of this species as a possible host plant needs further investigation.

Economic Significance
Euaresta stelligera is not known to be economically important. It presumably may reduce seed or pollen production by A. chamissonis, but the latter, commonly known as beach bur, is not a major weed or important source of allergic pollen (Goeden & Ricker 1974).

Comments
Berlocher (1984b) presented electrophoretic evidence that E. stelligera, previously considered a synonym of E. bellula, is a distinct species. This was based on analysis of a population of E. stelligera from Oregon and a population of E. bellula from New Mexico. He also listed several morphological differences between these two populations, although of those only the difference in genal height appears to be fully diagnostic. There is little difference in aculeus tip length, but generally in E. stelligera the tip tapers more rapidly and is less triangular than in most E. bellula. The difference in abdominal microtrichial pattern also supports the hypothesis that these two species are distinct.

The status of the Colorado population (see Distribution) should be further investigated.

References
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Aldrich, J. M. 1905. A catalog of North American Diptera (or two-winged flies). Smithson. Misc. Collect. 46 (2): 680 p. [p. 605, in catalog]
Coquillett, D. W. 1894. New North American Trypetidae. Can. Entomol. 26: 71-75. [p. 74, description]
Berlocher, S.H. 1984. Electrophoretic evidence for the validity of Euaresta stelligera Coquillett (Diptera: Tephritidae). Journal of the Kansas Entomological Society 57: 354-357. [p. 354, electrophoresis, resurrection from synonymy]
Forsell, M. J. 1947. The Tephritidae of the Puget Sound region. Northwest Sci. 21: 167. [Washington]
Goeden, R. D. & D. W. Ricker. 1974. The phytophagous insect fauna of the ragweed, Ambrosia chamissonis, in southern California. Environ. Entomol. 3: 835-839.
Goeden, R. D. & D. W. Ricker. 1976. The phytophagous insect faunas of the ragweeds, Ambrosia chenopodiifolia, Ambrosia eriocentra, Ambrosia ilicifolia in southern California. Environ. Entomol. 5: 923-930.
Norrbom, A. L., L. E. Carroll, F. C. Thompson, I. M. White & A. Freidberg. 1999. Systematic database of names, pp. 65-251. In F. C. Thompson (ed.), Fruit Fly Expert Identification System and Systematic Information Database. Myia (1998) 9, vii + 524 pp. & Diptera Data Dissemination Disk (CD-ROM) (1998) 1. [p. 145, in catalog]
Quisenberry, B. F. 1950. The genus Euaresta in the United States (Diptera: Tephritidae. J. N.Y. Entomol. Soc. 58: 9-38. [p. 30, synonymy with E. bellula]

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