|scientific name Glyptoscelis squamulata |
common name Grape Bud Beetle
Woody shrubs and trees. Specimens have been found in pine, fir trees, as well as willow (Blake 1967).
Found between March and July. Peak emergence occurs near the end of March in California, but they have been found in the area as early as January (Stern & Johnson 1984).
6.5-10 mm in length, 3.3-5 mm in width. Oval or oblong shape, as is typical within the genus and family. Bronze-black body with pale creamy brown setae all over. Head with a distinct median line ending in a depression in the middle front. The antennae extend below humeri, and the seventh joint is long. The elytra are faintly depressed about the scutellum and have transverse depression below the intrahumeral sulcus. The prothorax is wider than long, also pubescent, with setae set vertically in the centre, and horizontally near margins. Prothorax is deeply punctate. The pronotum lacks a pattern of brown setae, and the elytra is lacking lines of brown setae, present in other species. The ventral side is covered in finer, hair-like setae, white in colour. Piceous surface completely hidden by hair. This, along with the lack of brown markings on the dorsal side creates an overall snowy white colour, diagnostic of the species. The legs are a dark reddish-brown colour (Blake 1967).
Species is very active at night, mostly sedentary during the day. Even when active, this species is rarely spotted flying. Instead, adults move by climbing along host plants, only flying when necessary. There is little to no sexual dimorphism within the genus, and as such there is not a reliable method of sexing adults. Egg clusters are deposited in and under the bark of Vitis vinifera, or table grapes, as well as other host plants. After hatching, larvae drop to the ground and enter the soil, were they mature and may overwinter. Eggs are laid in batches of 12 to 44 eggs at a time, and females can lay multiple batches of eggs without mating each time. The males are extremely aggressive in courtship, and often engage in mate guarding post-copulation. Males have been recorded to remain mounted on females for 4-5 hours, which interferes with subsequent oviposition by females. As such, females tend to reproduce less when in the extended company of males (Blake 1967, Bentley 2009, Stern & Johnson 1984).
Nothing indicating that specimens are rare. Beetles are commonly found in California and adjacent US states.
Adults eat plant buds and immature leaves of a variety of plants. Larvae feed on the roots of host plant underground (Stern & Johnson 1984).
From Canada to Chile, but primarily in the western United States (Blake 1967). The majority of the Strickland Museum specimens were collected in California, a few were collected in southern Alberta, in the Medicine Hat area.
This species is now considered a minor pest on table grapes (Bentley 2009), but between the 1920s-40s, it was a significant pest in Coachella Valley, California (Stern & Johnson 1984). Species has been controlled by Phosmet, dimethoate, and azinphosmethyl. The use of DDT in the 1950s is thought to have also curbed populations. Glyptoscelis squamulata also glows bright silver-blue under UV light, even when dead (Stern & Johnson 1984).
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