urticating hair
urticating bristle
urticaceous hair

Several lepidopteran families include species whose larvae bear urticaceous hairs.

However, many species whose larvae are armed with such hairs have behavioral patterns adapted to present the urticaceous hairs as a defensive threat and to inflict them on any perceived attackers.

Many other species of larvae lack any such localized concentrations of hairs and are armed more generally with urticaceous hairs; even so, they too will lash about frantically if disturbed, making them difficult to handle without suitable equipment.