Siphunculata (Anoplura; Sucking Lice)
Apterous insects living as ectoparasites of mammals. Eyes reduced or absent. Ocelli absent. Antennae 3- to 5-segmented. Mouthparts highly modified for piercing and sucking, retracted within the head when not in use. Thoracic segments fused; tarsi i -segme
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SIPHUNCULATA (ANOPLURA; SUCKING LICE) Apterous insects living as ectoparasites of mammals. Eyes reduced or absent. Ocelli absent. Antennae 3- to s-segmented. Mouthparts highly modified for piercing and sucking, retracted within the head when not in use. Thoracic segments fused; tarsi 1-segmented, claws single. Thoracic spiracles dorsal. Cerci absent. Metamorphosis slight.
The insects included in this order are exClusively blood-sucking ectoparasites of mammals and about 300 species have been described. Of these, two species infest man and about a dozen occur on domestic animals; the remainder have been taken from several orders of mammals including monkeys, rabbits, mice, seals, elephants, etc. There is no doubt that a great number of species are still undescribed. As in the Mallophaga (q.v.) there is considerable host-specificity and closely related host species tend to be infested by similar Siphunculates, e.g. Enderleinellus is restricted to squirrels (Sciuridae) and Pedicinus to the Cynomorph monkeys. A comprehensive and critical review of Siphunculate host-relations is given by Hopkins (1949) while Webb ( 1949) has discussed phylogenetic aspects of the host-parasite association for the lice of Ferungulate mammals. Kellogg (1913) pointed out the close physiological relationships between certain of these parasites and the specific blood-characters of their hosts as determined by precipitin tests and it is possible that a lethal effect of abnormal host-blood on the essential symbiotic bacteria which occur in most Siphunculates is a factor helping to determine host-specificity. The best known species of Siphunculata is Pediculus human us, the common louse of man (Fig. 312). It infests people living under unhygienic conditions and who go for a number of days without change of clothing. This insect exists in at least two forms which have been regarded as separate species; they are P. humanus capitis, the head louse, and P. humanus corporis, the body louse. A detailed comparison of the two forms has been made by Busvine (1948) and earlier workers, whose results, however, do not coincide in all details. Morphologically, populations of the two forms differ significantly in total body size, head dimensions and antenna} length, the body O. W. Richards et al., Imms’ General Textbook of Entomology © O. W. Richards and R. G. Davies 1977
SIPHUNCULATA (ANOPLURA; SUCKING LICE)
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louse being larger with a larger head and longer antennae though there is appreciable overlapping in the frequency distributions of the measurements. Biologically they differ in that body lice live between the clothes and skin of the infested person and are more resistant to starvation than the form capitis which is confined to the hair of the head. The two forms breed together readily under experimental conditions, the fertile hybrids being mor-
F 1 G. 312
A. Body louse (Pediculus humanus), female. B. Female hog louse (Haematopinus suis). C. Extremity of leg of Haematopinus suis. D. Egg attached to a bristle (H. suis) t, tarsus; tb, tibia; pr
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