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Arthropoda: Insecta

PHTHIRAPTERA KEY

("Anoplura" = Sucking Lice)

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[See: Phthiraptera Details]

Phthiraptera (= Anoplura) are the sucking or true lice that are ectoparasitic on mammals (primates, ungulates, canines and rodents). Most important on humans are the head louse, body louse and crab louse. The evolution of these lice with their hosts is closely paralleled. They are small wingless insects that live entirely as ectoparasites on mammals and birds and in the clothing of humans. Their mouthparts are adapted for piercing the skin and sucking the blood of their hosts. The eyes are poorly developed or absent, and there are no ocelli. Antennae are very short with 3-5 joints. The legs are very short and the single-jointed tarsus carries a large curved claw that is well adapted for clinging to the host. The thoracic segments are fused, and a flattened abdomen of nine segments has large pleural areas allowing the body to swell on feeding. There is no metamorphosis.

. The mouthparts are adapted for piercing and sucking blood. The biting lice, Mallophaga, that are not of great medical importance to humans, have chewing mouthparts that feed on scales, feathers, and skin waste (Matheson 1950).

Sucking lice are all permanent ectoparasites of mammals. They have highly modified mouthparts, which when at rest are pulled back within a diverticulum that opens into the lower part of the pharynx at its anterior end. The thoracic segments are fused save for the genus Haematomysus. The tarsi have only one segment and end in a single claw that is adapted for grasping and clinging to hair. Eggs are attached to the host's hair (Fig. 4). [Also see: Phthiraptera Details]

Phthiraptera is a small group of insects with about 230 species. They are all bloodsucking ectoparasites of mammals, and among the four families only the Pediculidae have species that are of medical importance to humans. The following key distinguishes these families:

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1. The head is extended in the form of a narrow tube. The tibia lacks a thumb shaped process opposing the claw, and the prothorax is very distinct. One species, Haematomyzus elephantis, feeds on elephants _ _ _ _ _ _ _ _ _ _ _ Haematomyzidae

2

The head is not extended The tibia has a thumb shaped process opposing the claw, & the prothorax is not distinctive (Fig. 1)

3

2. The overall body is definitely flattened, and it is lightly covered with setae or spines arranged in irregular rows. Species are parasitic on terrestrial mammals (Fig. 2) _ _

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The body is thicker and solid. It is more thoroughly covered with setae or spines that are arranged in more regular rows. Species only parasitize mammals in marine environments _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Echinophtheriidae

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3. There are pigmented eyes present. The head is not withdrawn into the thorax. Species are parasitic on humans and simians (Fig. 2 & Fig. 3) _ _ _ Pediculidae

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The eyes are vestigial or absent. The head is withdrawn deep into the thorax. The family has most of the described lice species _ _ _ _ _ _ _ _ _ Haematopinidae

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Key References: <medvet.ref.htm> <Hexapoda>

Burgess, I. F. 1998. Head lice: developing a practical approach. The Practitioner 242: 126-69.

Burgess, I. F. 2004. Lice and their control. Ann. Rev. Ent. 49: 457-81.

Burgess, I. F., C. M. Brown & P. N. Lee. 2005. Treatment of head louse infestation with 4% dimeticone lotion: randomised controlled equivalence trial.

BMJ 330: 1423-25.

Buxton, P. A. 1948. The Louse: An Account of the Lice which Infest Man, Their Medical Importance & Control, 2nd ed., Edward Arnold, London.

Chetwyn, K. N. 1996. An overview of mass disinfestation procedures as a means to prevent epidemic typhus. IN: Proc. 2nd Intern. Conf. on Insect

Pests in the Urban Environment. ICIPUE: pp 421-416.

Matheson, R. 1950. Medical Entomology. Comstock Publ. Co, Inc. 610 p.

Service, M. 2008. Medical Entomology For Students. Cambridge Univ. Press. 289 p

Meinking, T., C. N. Burkhart & C. G. Burkhart. 1999. Ectoparasitic diseases in dermatology: reassessment of scabies and pediculosis. Adv.

Dermatology 15: 77-108.

Nuttall, G. H. G. 1917. The biology of Pediculus humanus. Parasitology 10: 80-185.

Orkin, M. & H. I. Maibach (eds.). 1985. Cutaneous Infestations & Insect Bites. Marcel Dekker, NY., Chapt. 19-26.

Service, M. W. (ed.). 2001. The Encyclopedia of Arthropod-transmitted Infections of Man & Domesticated Animals. CABI: pp. 70-3, 170-4, 295-9.

Zinsser, H. 1935. Rats, lice and history. Boston Globe.

Zinsser, H. 1937. The rickettsia diseases: varieties, epidemiology and geographical distribution. Amer. J. Hyg. 25: 430-63.