African-black-beetle African-lawn-beetle appearance beetle black black-beetle bug color colour destructive granit-background granite hard hardy hemiptera heteronychus-arator insect lawn-infestations lawns legs persistent pest species surface beach coast coastline colored colors coloured colours layers levels ocean pebbles rocks rocky rough sand sea seashore seaside shade shadows shapes shore shoreline Sizes stones stony sunlight sunshine variety water Australian breeding burrows control damage damaging danger devastating digging ecosystem environmental erosion fauna feral invasive mammal mammalian pest pest control populated prolific rabbits reproductive spread threat uncontrollable widespread wild wildlife Bird watchers bird watching birders cliffs Cornish cornwall discovered England english find found Great Britain hobby natural nature observe ornithologists ornithology pastime people point study tide waves