Al-Hurr bin al-Sayyah (may Allah have mercy on him) said: I heard Ibn Umar (may Allah be pleased with him) say about a louse that a person in ihram kills: He should give in charity a piece of bread or a handful of food. [Sahih: Recorded by Ibn al-Ja'd: 570]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10067