G. H. F. Nuttall 
339 
1914. Neumann and Mayer, PI. XLIV, figs. 20, 21 ( humanus $), good. 
1915. Wulker, 1 text-fig. (humanus), progressive stages of development of the embryo 
in the egg, good. 
1915. Hase, 47 figs. ( cajpitis and corporis) mostly crude; good photographs showing im¬ 
mediate effects of bites in producing wheals. 
1916. Harrison, PI. VII, 7 text-figs, (corporis), mouthparts. 
1916. Peacock, text-figs. 1-8 (corporis), schematic, anatomy, also 1918, PI. VI. 6 text-figs. 
(corporis), mouthparts; taken in conjunction with Harrison’s, these are the best 
figures hitherto published. 
iv. 1916. Sikora, 3 PI. (2 coloured) and 24 text-figs, (corporis), important; also ix. 1917, 
3 text-figs., capitis and corporis compared. 
1917. Nuttall, Pis. Ill, IV, and 12 text-figs, (corporis), copulation and copulatory organs ; 
also 1918, Pis. I—III, and 12 text-figs, (corporis), biology and morphology; also 
ii. 1919, PI. X (corporis), showing pigmentation when raised on black background 
in contrast to white; also Keilin and Nuttall, Pis. XII-XVIII, text-figs. 1-28 
(capitis, corporis and crosses between the two), normal, abnormal, and hermaphro¬ 
ditic specimens; their external and internal anatomy. 
1919. Lloyd, figs. 1, 3, 5 (corporis), $ in dorsal aspect (poor), internal anatomy (diagram¬ 
matic), eggs. 
Considerations relating to the foregoing Synonymy. 
1. Valid and invalid names. 
The name Pediculus humanus was applied by Linnaeus (1758) to both 
head-lice and body-lice. He subsequently regarded head- and body-lice as 
two varieties of P. humanus , numbering them 1 and 2. Whilst de Geer (1778) 
inclined to the view that head-lice and body-lice were distinct species, or 
possibly varieties, he expressed no definite opinion either way, but suggested 
the names Pediculus humanus capitis and Pediculus humanus corporis whereby 
to distinguish the two forms. 
Latreille (1803) raised the two varieties of Linnaeus to specific rank, 
restricted the name Pediculus humanus to body-lice, and gave the name 
Pediculus cervicalis to head-lice. Therefore, if body-lice and head-lice con¬ 
stituted distinct species, their names would be respectively P. humanus and 
P. capitis, corporis falling into the synonymy of the former and cervicalis into 
that of the latter in accordance with the rule of priority. If on the other hand 
body-lice and head-lice are not regarded as two species but merely as varieties 
or races of one species, we are justified by the rules of zoological nomenclature 
in reviving the binomial of de Geer whilst more clearly defining its significance, 
a matter he left in doubt. 
In view of all the evidence at hand, which will be considered presently; 
I conclude, as already stated in my earlier papers, that P. humanus stands as 
a species and that it includes two races to which de Geer’s names capitis and 
corporis should be applied. It is in this sense that these names are employed 
hereinafter by me. 
The names P. tahescentium Alt 1824, and P. vestimenti Nitzsch 1818, 
