Which order contains insects commonly known as lice?

The order that contains insects commonly known as lice is Mallophaga. Lice are small, wingless parasites that typically infest the hair or feathers of their hosts. The two main types of lice are chewing lice (Mallophaga), which feed on skin debris and other organic material, and sucking lice (Anoplura), which feed on the blood of their hosts.

Mallophaga is specifically characterized by its members having chewing mouthparts, which differentiate them from other parasitic insects. This order is significant in both veterinary and medical contexts, especially in relation to the health of birds and mammals, including humans.

Other options are distinguished by different characteristics: Siphonaptera is the order that includes fleas, which are also blood-feeding parasites, but they have a different feeding mechanism and body structure. Hymenoptera includes a diverse group of insects such as bees, ants, and wasps, which are primarily known for their social behavior and not for parasitism. Dictyoptera encompasses insects like cockroaches and mantids, which do not include lice. Thus, Mallophaga is the correct answer as it represents the specific order of insects known to be lice.