Larinus obtusus
In 3 days ~10% in a week ~20%
Larinus obtusus is a species of true weevil known as the blunt knapweed flower weevil. It is used as an agent of biological pest control against noxious knapweeds, especially spotted knapweed (Centaurea maculosa). The adult weevil is dark brown with a large, bulbous snout. It is 5 to 7 millimeters (0.19 to 0.27 inches) long in total. It is active throughout the summer when the female lays yellow eggs in the opened flower head. The larva emerges and feeds on the developing seeds inside the head. The larval stage lasts 17 days, after which the larva constructs a cocoon from the remnants of the seeds and pupates within it for about nine days. Most of the damage to the plant is done by the larva's feeding on the seeds; the adult feeds on the foliage but does less drastic damage to the plant. The average lifespan of the weevil is around 94 days for males and 58 for females.
This weevil is native to Europe and the Middle East. It was first introduced to the United States for the biocontrol of knapweeds in the Boulder, Colorado area in 1991. It is now established in much of the northwestern United States, but its abundance is unknown. This weevil is quite similar to its relative, Larinus minutus, which is also a knapweed specialist used for biocontrol. They are currently considered separate species but this could change with further research. Wikipedia →
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More parks will be added in future updates.
Rare
Under 5% of wildlife watchers report a Blunt Knapweed Flower Weevil sighting in Boston on a given day, based on 16 verified sightings from GBIF citizen-science data. It is the 565th most-seen of the 1200 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
July
In that month about 10% of wildlife watchers report a Blunt Knapweed Flower Weevil in Boston on a given day, against under 5% in August to June, the lowest months.
2nd of 5
Of the 5 cities where we can rate Blunt Knapweed Flower Weevil sightings, Boston ranks 2nd at under 5%. The best odds are in Munich (Germany, about 10%).
Same family: Curculionidae
The closest relatives of the Blunt Knapweed Flower Weevil that you can see in Boston (family Curculionidae, True Weevils) are Peach Root Weevil (about 10%), Green Immigrant Leaf Weevil (about 10%) and Asian Oak Weevil (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Blunt Knapweed Flower Weevil is recorded against all the insects logged in Boston (16 verified sightings), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
