Are aphids a kind of lice?

No, aphids are not a kind of lice even though their activities are somewhat lice-like and even though they get called plant lice. Lice of the Phthiraptera insect order technically function as disease-vectoring, obligate insect parasites of warm-blooded hosts whose blood and secretions they drink as members of sipping species or whose debris and skin they feed upon as chewing species members. Aphids of the Hemiptera insect order pierce leaf, stalk and stem tissue to access internal, life-sustaining, nutrient-rich xylem and sugar-rich phloem and thereby vector diseases and pathogens.