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Studies on populations of head-lice (Pediculus humanus capitis: Anoplura)

IV. The compositions of populations

Published online by Cambridge University Press:  06 April 2009

P. A. Buxton
P. A. Buxton
Affiliation:
From the London School of Hygiene and Tropical Medicine
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1. In three previous papers (1936, 1938b, 1940a) the author has discussed the distribution of head-lice among their human hosts, his material being nearly 3000 complete crops of hair. The present paper deals with the strictly entomological side of the inquiry, that is to say, with the study of the populations of head-lice themselves. The total amount of material is the lice from 858 infestations from six places; from each of four places there were less than 100 infestations.

2. In about two-thirds of the infestations there were ten lice or less, the proportion of low infestations varying considerably from place to place (Table 1). Infestations over 100 never formed more than 10% of all the infestations in a place.

3. In a single head the proportion of the sexes is often far from equal; indeed, in light infestations it is common to find that all the adults are of one sex. Taking all the heads from one place, the total number of males and females differs significantly from equality, an excess of males occurring in one place, of females in another (Table 2). In all heads from one place the coefficient of correlation between the number of males and females is high, about 0·8–0·9. As the density of the louse population, does not generally affect the sex ratio, the correlation is approximately linear. But when the density is unusually high, as it is in some heads from Colombo, the proportion of males rises progressively. This is the only case known, in spite of much searching, in which sex ratio of the louse is affected by an environmental factor.

4. In the matter of the number of larvae per female, there are great individual differences between heads, though the coefficient of correlation, worked on all the heads from one place is as high as 0·7 or 0·9. Taking all the heads from one place, the mean number of larvae per female ranges between 5·4 and 10·9; many of the differences between places are significant. I have failed to find any explanation of these differences, and they do not seem to be affected by any environmental factor. The fact that the larvae are always more numerous than the females, indicates that there is a high mortality during the course of larval life; the author has failed to make a more precise estimate of the proportion which die.

5. A small part of the material was specially examined, and every larva referred to its instar. In this sample of 502 larvae it was found that the death-rate was higher in the third instar than in the other two, a state of affairs the reverse of what occurs in body-lice reared in boxes.

Type
Research Article
Information
Parasitology , Volume 33 , Issue 2 , May 1941 , pp. 224 - 242
Copyright
Copyright Cambridge University Press 1941

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References

REFERENCES

Awati, P. R. (1922). Survey of biting insects of Assam with reference to kala-azar for the whole year from November 1921 to October 1922. Biting insects found in dwelling houses. Ind. J. Med. Res. 10, 579–91.Google Scholar
Buxton, P. A. (1936). Studies on populations of head-lice (Pediculus humanus capitis: Anoplura). I. Parasitology, 28, 92–7.CrossRefGoogle Scholar
Buxton, P. A. (1937). The numbers of males and females in natural populations of head-lice (Pedieidus: Anoplura). Proc. R. Ent. Soc. Lond. Ser. A, 12, 12–14.Google Scholar
Buxton, P. A. (1938 a). Studies on the growth of Pediculus (Anoplura). Parasitology, 30, 65–84.CrossRefGoogle Scholar
Buxton, P. A. (1938 b). Studies on populations of head-lice (Pediculus humanus capitis: Anoplura). II. Parasitology, 30, 85–110.CrossRefGoogle Scholar
Buxton, P. A. (1940 a). Studies on populations of head-lice (Pediculus humanus capitis: Anoplura). III. Material from South India. Parasitology, 32, 296–302.CrossRefGoogle Scholar
Buxton, P. A. (1940 b). The biology of the body louse (Pediculus humanus corporis: Anoplura) under experimental conditions. Parasitology, 32, 303–12.CrossRefGoogle Scholar
Cannon, H. G. (1922). A further account of the spermatogenesis of lice. Quart. J. micr. Sci. 66, n.s. 657–67.Google Scholar
Doncaster, L. & Cannon, H. G. (1920). On the spermatogenesis of the louse (Pediculus corporis and P. capitis), with some observations on the maturation of the egg. Quart. J. micr. Sci. 64, n.s. 303–28.Google Scholar
Holdaway, F. G. (1932). An experimental study of the growth of populations of the “flour beetle” Tribolium confusum Duval, as affected by atmospheric moisture. Ecol. Monogr. 2, 261–304.CrossRefGoogle Scholar
Holdaway, F. G., & Smith, H. F. (1933). Alteration of sex ratio in the “flour beetle” Tribolium confusum Duval, following starvation of newly hatched larvae. Aust. J. exp. Biol. med. Sci. 11, 35–43.CrossRefGoogle Scholar
Keilin, D. & Nuttall, G. H. F. (1919). Hermaphroditism and other abnormalities in Pediculus humanus. Parasitology, 11, 279–328.CrossRefGoogle Scholar
Nuttall, G. H. F. (1917). The biology of Pediculus humanus. Parasitology, 10, 80–185.CrossRefGoogle Scholar
Nuttall, G. H. F. (1919). The biology of Pediculus humanus. Supplementary Notes. Parasitology, 11, 201–20.CrossRefGoogle Scholar
Wigglesworth, V. B. (1939). The Principles of Insect Physiology. London: Methuen.Google Scholar