PHILADELPHIA—Customs agents seized more than two dozen giant beetles—some the size of a child’s hand—from an overseas package after postal workers heard the insects making scratching noises.

The large bugs arrived last week from Taiwan at a post office in Mohnton, about 50 miles northwest of Philadelphia, in a box whose contents were labeled as toys, gifts and jellies, officials said Wednesday.

But the postmaster suspected the package contained live organisms and notified authorities. The package was sent to Philadelphia, where it was X-rayed and then opened.

“They are highly destructive insect pests that can cause extensive damage to fruit and vegetable crops, trees, shrubs and turf grasses,” John Plummer, an agency agriculture specialist, said in a statement Wednesday.