There is considerable argument to suggest that the Sucking Lice (Siphunculata) and the Biting Lice (Mallophaga) are part of a single order the 'Anoplura' and you may find that what I have treated as two separate orders here, are classified as two suborders under the common title of 'Anoplura' elsewhere. Unless you are a taxonomist or very seriously studying these insects it is not important to make a decision which form of classification you prefer.
The Siphunculata are described as wingless (Apterous), hemimetabolous (having a simple metamorphosis i.e. no pupa) ectoparsites (living on the outside of their hosts) of mammals, there are about 300 described species of which 24 are found in Britain. They have reduced or absent compound eyes, no ocelli and no cerci. The mouthparts are adapted for sucking and retractable into a special cavity in the head when not being used. They are dorsoventrally flattened with strengthened legs which have large single claws and only a single tarsal segment as part of their special adaptation to clinging on.
Sucking Lice all feed on fresh blood and only occur on Mammals, they are of most importance to mankind because of the ones that live on us. There are two species which feed only on humans, Phthirus pubis the Pubic Louse which is the squatter, broader and more sedentary of the two and can be distinguished by its having unequal legs, (the fore legs being shorter and weaker), and Pediculus humanus. Pediculus humanus has two races 'capitis' (or the Head Louse) which lives on the head and is believed to be the original form and 'corporis' (or the Body Louse) which lives on or in clothes and around the body and is believed to have evolved from the former.
The family Pediculidae is restricted to primates as its hosts and always has eyes which are prominent and pigmented, Pedicularis humanus race corporis is the carrier of Ryckettsia prowazeki the cause of Typhus which is transmitted in the faeces of the louse.
The eggs are oval and whitish when first layed, they are glued by the female louse onto the hair or skin of the host (in most species P, humanus sometimes just scatters it eggs around its hosts body) by a drop of louse glue, this is a clear fast drying glue exuded by the female before laying the egg. A female will lay about 300 eggs at about 10 eggs a day. The eggs take 8 days to hatch in P. humanus and 12 days in Haematopinus eurysternus a louse of ungulates (hooved mammals). There are three larval instars which take 16 to 19 days to become adult in P. humanus and 12 days in Haematopinus eurysternus. There is then a further period of 1 to 3 days before the new adults become sexually mature.
The taxonomy of the Siphunculata is still in considerable confusion as reguards the higher classification and what is below may be different to what you will find in texts other than Imms.