Chaetorellia acrolophi
Insect (Diptera: Tephritidae)
knapweed peacock fly

Photos: Adult

   Chaetorellia acrolophi
Photo by: . -Larva

Common names: Knapweed peacock fly. (1)
Origin: Northeastern France, eastern Austria, Switzerland, Romania, and Hungary (1)

Life cycle:
Over wintering stage: Within the seed head as a third-instar larva. (1)
Egg stage: In the beginning of May, in the Swiss Valais, eggs are found in the field.  Under unopened buds eggs are laid in batches of two or four.  They are also laid singly.  The eggs usually hatch within four to five days.  They measure about 0.9 mm long and 0.2 mm wide.  They are elongate, shiny white, and have a long filament that is thick at one end. (1)
Larval stage: There are three larval instars for this fly.  The first-instar burrows, after hatching, into the center of the bud in a horizontal path.  They make their way to the seed, eating the young florets on the way.  The second- and third-instar larvae eats the florets, developing seed, and a little on the receptacle.  They completed the larval stage in 10 to 15 days.  While a larvae they are white in all three stages. (1)
Pupil stage:  Pupa are usually in a white puparium form with some plant hairs or florets stuck to the surface of this pupa.  The pupa is usually positioned vertically between the florets in the apical region of the flower head. (1)
Adult stage: Adults are present from mid May until mid August in the Swiss Valais.  In Austria the flies are present from mid June to mid November.  Adults can live up to four weeks in a lab.  Mating is usually immediately after emergence.  The females usually lay eggs after two days of emergence.  The adults are orange yellow and may have spotting on the abdomen and the thorax.  They grow to be four to five millimeters long.  They have brown bands on their clear wings. (1)

Destructive stages: Larval (1)
Plant species attacked: Spotted knapweed (Centaurea maculosa), purple starthistle (C. calcitrapa), diffuse knapweed (C. diffusa), C. luecophaea, C. vallesiaca, and C. virgata. (1)
Site of attack: Within the seed head is where the larvae feed. (1)
Damage to host: Feeding on the seed heads can reduce seed production.  Even one single larva can consume all of the seeds in a single flower head. (1)

First introduced into the United States: Montana 1992 (1)
Now established in: Montana and Oregon (1)
Habitat: place where knapweed plants are (1)
Availability: Not available for general redistribution. (1)
Stage to transfer: Adult and larval. (1)
Redistribution: In the late fall infested seed heads are collected and stored at 4 to 8o C until the next spring.  In the spring the seed heads are put into sleeve boxes at room temperature.  Soon after emergence, the adults are released after being identified.  To ship the larvae you would ship them while the larvae is still in the seed head.  Or, ship the pupa that has been removed from the seed heads. This is much easier than shipping the adults.(1)

Comments: This fly is only one of  six different species that feed on the knapweed flower and the seed heads. In Eurasia, Chaetorelli acrolophi coexist with Terellia virens (which were released in 1992 in the USA), U. quadrifasciata, Metzneria paucipunctella, Urophora affinis, and Bangasternus fausti (all released in the USA). Each of the organisms have their individual characteristics to pick different host plants and a place where the climate is to their satisfaction.  To find a new place to release captured insects to fight against noxious weeds may be difficult.  For many years into the future C. acrolophi may become more common.  After these several years the production of noxious weeds should decrease. (1)

 This is the total amount of links we were able to locate.  If you find more pictures or links, please e-mail them
1)   Rees, Normal, et. al., Ed., Biological Control of Weeds in the West, Western Society of Weeds Science, in Cooperation With USDA ARS, Mt Department of Ag, and MT State Univ., Color World Printers, Bozeman Mt, Feb., 1996.

by: Sandra Doris, Carolyn McKinney, and Kaycee Howser, 02/03.
Updated by: Amanda Reed and Ua Ita, 02/22/09.

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