Life history of Larinus minutus (Coleoptera: Curculionidae), a biological control agent of spotted knapweed

Life history of Larinus minutus (Coleoptera: Curculionidae), a biological control agent of spotted knapweed

Larinus minutus was first introduced to North America in 1991 as a biological control agent of invasive knapweeds and has since then become established in several states and provinces.  Despite the widespread use of this insect, little is known about the developmental rates or activity patters of this species other than a generalized life history.  Pyramid traps (18) were placed in a field to evaluate L. minutus emergence from overwintering sites.  In order to better describe the development of L. minutus, 650 weevils were collected from a spotted knapweed plot established at the University of Arkansas Agriculture Experiment Station and allowed to mate for 2 days at 25°C with a 16L:8D photoperiod.  Females were removed and placed individually in an individual mesh bag attached to a capitulum.  Females were allowed approximately 24 hours to oviposit on the enclosed capitulum.  Caged capitula (20) were dissected biweekly and larval instar determined to delineate development times for each L. minutus instar.  Adults emerged from overwintering sites approximately 30 days earlier than in previously published studies.  Larval development studies are ongoing, with egg hatch occurring in approximately 5 days, which is consistent with previously published reports.