Original: Lice (singular: louse), (order Phthiraptera), also known as fly babies or Nits, are an order of over 3,000 species of wingless insects; three of which are classified as human disease agents.
Simplified: Lice (singular: louse), (order Phthiraptera) are an order of  wingless insects. There are more than  3,000 different species; three are classified as human disease agents.