Oulema melanopus
In 3 days ~10%
The cereal leaf beetle (Oulema melanopus) is a significant crop pest, described by Carl Linnaeus in 1758. One generation of this beetle is produced a year. Adults feed before winter and spend most of their overwintering time in protected areas such as wind rows, crop stubble, and tree bark crevices. Adults mate once the temperature warms to above 9–10 degrees Celsius (or 44.6 degrees F) and females have a relatively long laying period (about 45–60 days), when they deposit eggs on the undersides of leaves. The larvae hatch in 7–15 days, and start the most damaging eating of the entire lifecycle. These larvae mature in 12–20 days. Larvae are the greatest threat to crops, as they eat the superficial layer of leaves, hindering the leaves' photosynthetic potential. According to Kon, Zabik, Webster, and Leavitt, a chemical factor attracts the beetles to leaves, and that chemical factor is directly related to hydrophobicity. Pupation occurs in soil, with the adults emerging in 20–25 days, ready to start the cycle again.
Eggs are cylindrical and round, about 0.9 mm long and 0.4 mm wide. Eggs are often laid along the midvein on the undersides of leaves. They are bright yellow... Wikipedia →
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Rare
Under 5% of wildlife watchers report a Cereal Leaf Beetle sighting in Toronto on a given day, based on 5 verified sightings from GBIF citizen-science data. It is the 1544th most-seen of the 1689 insects we can rate there. Over three days the chance rises to about 10%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Cereal Leaf Beetle in Toronto on a given day, so our monthly data shows no clear season.
Among the best
Of the 2 cities where we can rate Cereal Leaf Beetle sightings, Toronto ranks 2nd at under 5%, level with the leaders once rounded. The best odds are in Paris (France, under 5%).
Same family: Chrysomelidae
The closest relatives of the Cereal Leaf Beetle that you can see in Toronto (family Chrysomelidae, Leaf Beetles) are Spotted Cucumber Beetle (about 10%) and Goldenrod Leaf Beetle (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Cereal Leaf Beetle is recorded against all the insects logged in Toronto (5 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.
