Explanation of Names
robiniae = 'of Robinia' (refers to a host tree)
has all yellow elytral markings (1)
metepisternum (region betw. 2nd & 3rd hind leg) nearly completely covered in yellow pubescence (2)
widely dist., wherever people have planted Black Locust (Robinia pseudoacacia
Adults common on goldenrod Aug-Oct
Larvae feed on Black Locust (Robinia pseudoacacia
). (Honey Locust (Gleditsia triacanthos
) is not affected.)
Adults feed on pollen, particularly goldenrod (Solidago spp.).
Eggs are laid in the fall. Newly emerged larvae hibernate under bark, tunnel in spring, making tunnels about 10 cm long and 6 mm wide, pupate late Jul/early Aug; adults emerge late Aug-Sep.
Larva & pupa
Considered a serious pest of Black Locust; previously weakened or damaged trees are often killed by the larvae. Previously confined to the native range of Black Locust in the northeast, it has spread with the trees throughout the US and parts of Canada. Black Locust is used for reclamation and similar projects where trees are likely to be stressed and thus more vulnerable to damage.
Placosternus difficilis (Chevrolat)
- Range: so. US
sutural one-third of elytron with distinct, abrupt depression margined by a slight carina (or ridge) (2)