Larinus curtus

Distinguished from similar thistle-feeding weevils by its association with yellow starthistle (Centaurea solstitialis) rather than other thistle species. Differs from the thistle head weevil (Rhinocyllus conicus) and Canada thistle bud weevil (Larinus planus) by host plant specificity and geographic origin. The short snout relative to some congeners and specific habitat association with yellow starthistle aid in field identification.

Adult weevils are dark brown to black with light-colored mottled hairs covering the body. Body length is approximately 6 mm. The species possesses the characteristic elongated snout (rostrum) typical of the family Curculionidae. Females deposit glossy, milky white, oval-shaped eggs at the bases of open yellow starthistle flowers.

Associated with yellow starthistle (Centaurea solstitialis) infestations in grassland and rangeland ecosystems. In its native range, occurs in Mediterranean climates of southern Europe. In the introduced range, established in the Pacific Northwest and other regions where yellow starthistle occurs.

Native to southern Italy, southern Europe, the Middle East, and the Caucasus region. Introduced to the United States in 1992; now established throughout the Pacific Northwest in relatively low densities.

Adults emerge from overwintering diapause in spring. Egg-laying occurs over approximately 6-8 weeks during the flowering period of yellow starthistle. New adults emerge in late summer and enter diapause for winter. One generation per year (univoltine).

Specialized feeder on yellow starthistle (Centaurea solstitialis). Adults feed on flowers and pollen. Larvae develop within seed heads, feeding on developing seeds and pappus. Laboratory studies indicate minimal oviposition on safflower (Carthamus tinctorius) with no successful larval development; field reports of adult feeding on safflower flowers have been documented but larval establishment has not been confirmed.

• Centaurea solstitialis - primary hostyellow starthistle; required for larval development
• Carthamus tinctorius - tested hostsafflower; adults observed feeding in field, no confirmed larval development

Univoltine (one generation per year). Adults emerge from overwintering sites in spring. Females lay eggs at bases of open flowers. Larvae hatch within days, enter flower heads, and develop through three instars feeding on seeds. Pupation occurs within the seed head. New adults emerge in late summer, feed briefly, then enter diapause for winter. Average fecundity approximately 30-50 eggs per female under laboratory conditions.

Adults exhibit strong host fidelity to yellow starthistle. Females deposit eggs directly into flower heads. Larvae are capable of destroying all seeds within a single flower head. Adults feed on floral tissues but cause minimal direct damage to plant vigor compared to larval seed predation.

Biological control agent that reduces seed production of invasive yellow starthistle, potentially limiting spread and population density of this noxious weed in rangelands and agricultural areas. The 96% average seed reduction per infested flower head significantly impacts plant reproductive output.

Introduced intentionally to the United States in 1992 as a classical biological control agent for yellow starthistle, an invasive weed causing significant agricultural and ecological damage. Established populations contribute to integrated weed management programs, though densities remain relatively low in the Pacific Northwest. Concerns about potential non-target effects on native thistles and related crops (particularly safflower) have been investigated through host specificity testing.

• Larinus planusSimilar size and morphology; distinguished by host association with Canada thistle (Cirsium arvense) rather than yellow starthistle
• Rhinocyllus conicusAnother European weevil introduced for thistle biocontrol; differs in attacking multiple thistle species including native North American thistles, with broader host range and longer snout

• biological control
• invasive species management
• Curculionidae
• yellow starthistle
• seed predator
• classical biocontrol
• rangeland pest management
• Mediterranean native
• Pacific Northwest introduced
• host specificity

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
• Eaters of thistles: Thistle tortoise beetle, Cassida rubiginosa, and Canada thistle bud weevil, Larinus planus — Bug of the Week
• Dr. Jekyll and Mr. Hyde wage war on thistles: Thistle head weevils, Rhinocyllus conicus — Bug of the Week
• Archive — Bug of the Week
• Biology of Larinus curtus Hochhut (Coleoptera: Curculionidae), a European Weevil for Biological Control of Yellow Starthistle Centaurea solstitialis L (Asteraceae), in the United States
• A field experiment to determine host specificity of Larinus curtus Hochhut (Col., Curculionidae) and Urophora sirunaseva Hg. (Dipt., Tephritidae), candidates for the biological control of Centaurea solstitialis L. (Asteraceae), and Larinus minutus Gyllenhal, a candidate for biological control of C. maculosa Lam. and C. diffusa Lam.