28 
Rickettsia-^6 Parasite of Cimex 
masses inside the cells of the mid-gut of Pediculus humanus after the latter 
has fed on typhus patients. Although often present in large numbers free in 
the gut, it appears to multiply inside the epithelial cells. Wolbach and Todd 
(1920) have described similar forms in the tissues of human sufferers from 
typhus. The organism varies considerably in shape and size; usually it is 
round, diplococcal or oval, but often resembles short bacilli; thread forms also 
occur. 
(3) R. quintana or wolhynica, first described by Toepfer (1916) as the 
cause of trench fever, occurs in enormous numbers in the lumen of the gut of 
lice (P. humanus) which have fed on trench fever patients. It is more con¬ 
stantly rounded, oval or diplococcal than R. proivazeki and is not known to have 
occurred in thread forms. This species also stains a deeper purple by Giemsa’s 
method. Most writers agree that the organism does not occur inside cells. 
It may be identical with R. pediculi. 
(4) R. pediculi , first described by Munk and da Rocha-Lima (1917) as 
an occasional inhabitant of the gut of normal (uninfected) lice and subse¬ 
quently said by them to be present in trench fever lice. They say that it is 
indistinguishable from R. quintana. It seems probable that the supposedly 
normal lice in which the parasite has been found had fed upon convalescents 
from trench fever whose disease had not been diagnosed. 
(5) A species of Rickettsia found in lice which had fed on persons suffering 
from “war nephritis” was described by Toepfer (1917), who believed that he 
could distinguish it from R. prowazeki and R. quintana by its morphology. 
This has not been confirmed. 
(6) A form of Rickettsia which Munk and da Rocha-Lima (loc. cit.) found 
occasionally in a few batches of lice which had either fed on normal persons 
or on trench fever patients. Munk and da Rocha-Lima stated that the organism 
was larger and stained more deeply than R. prowazeki, that it occurred not 
only in the lumen of the gut but also inside the cells lining the alimentary 
canal, in contrast to R. pediculi and R. quintana. These writers also stated 
that the organism damaged the cells of the gut and interfered with the powers 
of the insect to digest blood; they believe it to be a special parasite of the 
insect and not to be associated with human disease. If Munk and da Rocha- 
Lima are correct in this opinion their organism resembles the next species 
and that found in A. lectularius, which is described in this paper, so far as 
restriction to the invertebrate host is concerned. 
(7) R. melophagi. This organism has been described by Noeller (1917), 
Sikora (1918), Jungmann (1918), and others, who say it is constantly present 
in the middle part of the stomach of Melophagus ovinus (the sheep “ked”), in 
large numbers in the older adults, in smaller numbers in young adults, and 
even occurs in pupae or in very young adults which have not yet sucked blood. 
The parasite is, they believe, hereditary in the “ked” and not derived from the 
sheep. The forms described are slightly larger than those of R. pediculi or 
R. prowazeki , round, oval or diplococcal in shape. Threads have not been 
