Eristalis brousii
Male
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Syrphidae
Genus: Eristalis
Species:
E. brousii
Binomial name
Eristalis brousii
Williston, 1882

Eristalis brousii, also known as the hourglass drone, is a fly species in the Syrphidae family. Aside from northern Canada, the species has been largely eradicated throughout its former range. American paleontologist and taxonomist Samuel Wendell Williston published the first official description of it in 1882.[1] Eristalis brousii are known as hoverflies, or flower flies, due to their often seen behavior of hovering and nectaring at flowers, where they obtain energy-restoring nectar and protein-rich pollen.[2] The larvae are rat-tailed aquatic filter-feeders.[3]

Description

Eristalis brousii is similar to Eristalis arbustorum, except for the coloration of the mesotibia (middle part of the tibia). In E. brousii, the mesotibia is yellow on the basal half, and reddish-brown to black on the basal tarsomere of the mesoleg, whereas in E. arbustorum the mesotibia is yellow on the basal third and the basal tarsomeres of the mesolegs are brown to black. E. brousii measures 9–12 mm (0.35–0.47 in) in length.

A drawing of the head of Eristalis brousii, seen from the side.
Eristalis brousii head

The frontal triangle is slightly shiny along the middle. In a female, the front is reddish pollinose and more shiny above the antennae. The face is black, shiny, thickly clothed with yellow pollen and pile, leaving the tubercle, the oral margin, and the cheeks shining black. The antennae are black with third joint (flagellum) somewhat reddish. The eyes are pilose and in the male contiguous for a short distance only. The arista is reddish and briefly pilose near the base. The posterior lateral orbits are white pollinose.

Thorax

The scutum is shining black and with a coppery luster. Two opaque, lighter-colored, rather broad stripes reach from the front to the scutellum. These are limited by three narrow, opaque, black stripes. The pile of the scutum is light reddish yellowish, scarcely apparent from above. The scutellum is subtranslucent yellowish or reddish on the outer part. The pile of the pleurae is whitish.

Wings

The wings are hyaline with a minutely brownish stigma. In females, the wings have a large faint brownish spot. Noteworthy veination - Spurious vein (sv), looping of R4+5 into r4+5, closed cell r2+3. Anterior cross-vein (r-m) near the middle of discal cell (dm), oblique.

Eristalis brousii abdomen

Abdomen

On the abdomen of a male, the first segment is all black, the second orange-yellow, broadly on the sides and narrowly across on the hind border, elsewhere opaque black; on the posterior, nearly a third of the width of the segment is black; the sides approach each other a little towards the front and then at nearly right angles extend outward along the anterior margin of the segment; the lateral prolongations are convex on their hind borders and reach acutely nearly to the lateral margins; third segment with large, similar colored spots, confluent with the yellow in front but rounded on the internal posterior angles and usually not quite reaching the yellow of the hind margins; across the middle of the segment a shining metallic band interrupted in the middle; elsewhere the black is opaque; fourth segment wholly shining, with a narrow yellow hind margin and sometimes with a small spot of opaque black in front; hypopygium shining black. In the female, the markings are rarely like those of the male, chiefly shining black; the second segment sometimes includes a small, opaque, red dish spot on the side, as in the male; the third and fourth segments sometimes have small opaque spot in front; on the second, third, and fourth segments, a rather broad, whitish pollinose may be located on the hind border; the hind margins are more narrowly reddish yellow.[4][5]

Distribution

The population of Eristalis brousii has suffered a large decline in North America since the introduction of the European species E. arbustorum near Toronto around 1885. Currently, E. brousii is only found along the lake margin of Hudson Bay.[4]

References

  1. ↑ Williston, S.W. (1887). "Synopsis of the North American Syrphidae". Bulletin of the United States National Museum. 31: 1–335.
  2. ↑ https://www.researchgate.net/profile/Wouter-Steenis/publication/376553556_The_flower_flies_Diptera_Syrphidae_of_Nebraska_USA_In_honour_of_F_C_Thompson/links/657c9f06aff8b16813a8e44d/The-flower-flies-Diptera-Syrphidae-of-Nebraska-USA-In-honour-of-F-C-Thompson.pdf
  3. ↑ Telford, H. S. (1970). "Eristalis (Diptera: Syrphidae) from America North of Mexico". Annals of the Entomological Society of America. 63 (5): 1201–1210. doi:10.1093/aesa/63.5.1201.
  4. 1 2 Skevington, Jeffrey H (2019). Field Guide to the Flower Flies of Northeastern North America. ISBN 9780691189406.
  5. ↑ Hull, Frank Montgomery (1925). "A Review of the Genus Eristalis Latreille in North America. Part II" (PDF). The Ohio Journal of Science. 25: 11–45.
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