oak processionary caterpillars travel in nose-to-tail processions

air allergic allergy animal bark bug butterfly caterpillar caterpillars closeup damage danger dangerous environment focus foliage forest hair hairs hairy hazard health infection infestation insect irritant irritating irritation line macro nature oak open outdoors pest poison poisonous procession processionary processionea queue row selective setae spring thaumetopoea toxic tree trees trunk venomous wildlife