Chaetorellia

Hendel, 1927

Species Guides

2

Chaetorellia is a of tephritid fruit flies ( Tephritidae) containing approximately 11 described . Species in this genus are on Asteraceae flower , with larvae developing within capitula and feeding on developing florets and seeds. Several species have been investigated or deployed as agents against thistles and knapweeds, particularly yellow starthistle (Centaurea solstitialis). The genus is characterized by distinctive morphological features and -specificity patterns that have been taxonomically revised.

Pronunciation

How to pronounce Chaetorellia: //ˌkiːtoʊˈrɛliə//

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Habitat

are associated with flower of Asteraceae plants, particularly members of tribes Cardueae (Cynareae). specificity is determined by plant distribution: agricultural fields for safflower-associated species (e.g., C. carthami), rangelands and grasslands for yellow starthistle and knapweed-associated species (e.g., C. australis, C. succinea, C. acrolophi), and disturbed habitats where weedy Centaurea and related occur.

Distribution

Palearctic region with native ranges in Europe, the Mediterranean Basin, and western Asia. Some have been introduced to North America for : C. australis was introduced to the western USA (Washington, Oregon, Idaho) beginning in 1988; C. succinea was unintentionally introduced and established in North America. GBIF records indicate presence in Denmark, Norway, and Sweden.

Seasonality

Varies by and climate. C. carthami in Iraq shows in late March to early April with (one per year) . C. australis is trivoltine (three generations per year). C. hexachaeta in northern Greece has at least three generations per year. Seasonal activity is tied to plant flowering phenology.

Diet

Larvae feed on developing florets and seeds within flower of Asteraceae plants. Specific host associations include: Centaurea solstitialis (yellow starthistle), Centaurea cyanus (cornflower), Carthamus tinctorius (safflower), Centaurea maculosa (spotted knapweed), and related Centaurea, Carthamus, and Chartolepis . C. hexachaeta larvae destroy on average 86.3% of achenes in attacked yellow starthistle flower heads.

Host Associations

  • Centaurea solstitialis - primary yellow starthistle; confirmed for C. australis, C. hexachaeta, C. succinea
  • Centaurea cyanus - cornflower; confirmed for C. australis
  • Carthamus tinctorius - safflower; primary for C. carthami, also accepted by C. hexachaeta in no-choice tests but rejected in two-choice tests with yellow starthistle
  • Centaurea maculosa - spotted knapweed; for C. acrolophi
  • Centaurea calcitrapa - purple starthistle; laboratory for C. succinea
  • Centaurea melitensis - Maltese starthistle; laboratory for C. succinea
  • Centaurea sulphurea - sulphur starthistle; laboratory for C. succinea
  • Silybum marianum - milk thistle; laboratory for C. succinea, also attacked by C. carthami in Iraq
  • Cirsium vulgare - non-bull thistle; laid in laboratory but larvae did not survive (C. hexachaeta)
  • Cirsium arvense - laboratory Canada thistle; C. succinea laboratory range
  • Cynara cardunculus - laboratory cardoon; C. succinea laboratory range
  • Cynara scolymus - laboratory artichoke; C. succinea laboratory range
  • Cichorium intybus - laboratory chicory; C. succinea laboratory range
  • Helianthus annuus - laboratory sunflower; C. succinea laboratory range
  • Centaurea stoebe ssp. micranthos - laboratory spotted knapweed; C. succinea laboratory range
  • Centaurea diffusa - laboratory diffuse knapweed; C. succinea laboratory range

Life Cycle

Development occurs entirely within Asteraceae flower . Females oviposit under bracts or into flower head tissue. Larval development takes place within the capitulum, feeding on developing florets and seeds. occurs either within the flower head (C. carthami) or in soil (C. carthami). time varies: C. carthami completes -to-egg development in approximately 20.2 days at 24–29°C. longevity is short: C. carthami males live 1.7 days, females 2.0 days under laboratory conditions; C. hexachaeta adults may live up to 60 days with females depositing up to 243 eggs. Voltinism ranges from (C. carthami) to trivoltine or multivoltine (C. australis, C. hexachaeta).

Behavior

Females of C. australis deposit a contact - immediately after oviposition by dragging the extended ovipositor over the floral bud surface. This deters subsequent oviposition by females for at least 10 days, reducing and . The pheromone also functions as a male arrestant, causing of males on frequently visited floral buds and facilitating sexual encounters. Under oviposition pressure or in no-choice laboratory conditions, females may deposit into non-host plants, but larval survival is typically absent or severely reduced on such plants.

Ecological Role

act as natural enemies (herbivores) of Asteraceae plants, with significant potential for of weeds. Larval feeding substantially reduces seed production: C. australis causes 83.4% reduction in seeds per capitulum with single , and 95.4% reduction with multiple larvae; C. hexachaeta destroys over 80% of achene production in attacked yellow starthistle . The contributes to top-down regulation of weedy Asteraceae and has been intentionally introduced for this purpose. - mediate and resource partitioning among patchily distributed flower heads.

Human Relevance

Several have been evaluated or deployed as agents against thistles. C. australis was introduced from Greece to the western USA in 1988 for control of yellow starthistle (Centaurea solstitialis) and has established at multiple sites in Washington, Oregon, and Idaho. C. acrolophi was described as a potential biocontrol agent for spotted knapweed and related Acrolophus species. C. hexachaeta was recommended for consideration as a biocontrol candidate but requires additional specificity studies. C. succinea was unintentionally introduced to North America and acts as a natural enemy of yellow starthistle. C. carthami was found to have minimal economic impact on safflower crops in Iraq (0.2% oil loss, 2.6% seed non-germinability). The illustrates both intentional and unintentional outcomes, with importance for risk assessment distinguishing laboratory versus realized host ranges.

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