32 
Rickettsia-Z/fe Parasite of Cimex 
The minute forms are also to be seen in some of the cells of teased guts in 
small numbers. In the cells of the seminal pocket on the ventral side of the 
fourth abdominal segment of adult females, known as the organ of Berlese 1 , 
and in the cells of the Malpighian tubes clusters of the lanceolate forms 
are of frequent occurrence, sometimes very large ones (Plate II, fig. 4), while 
the Rickettsia forms are frequently present in immense numbers in the en¬ 
larged cells of the tubes in company with the thread forms. There would seem, 
however, to be a distinction between the course of intracellular development 
in the two organs in that, so far as present observation goes, threads and rods 
are comparatively scarce in the organ of Berlese, whereas they are exceedingly 
plentiful in the infected Malpighian tubes, generally in excess of the Rickettsia 
bodies. The longer bacterial forms are often present in the cells of certain 
portions of the gut wall, but they are never very numerous in any one cell. 
Text-figure. Swelling in Malpighian tube of Cimex lectularius due to infection by the parasite. 
Camera lucida drawing from unmounted dissection of adult female. 
Within the cells of the Malpighian tubes the multiplication of the parasites 
becomes so great that individual cells are swollen to more than twice their 
normal diameter. This has only been observed in the larger nymphs or adult 
bugs. It is not uncommon to see two or more tubes each with one or more 
swellings in the same insect and as the tubes at these points may be two or 
even three times their normal diameter (Text-figure) the infection is quite 
apparent under the dissecting microscope. 
The enlarged cells in fresh preparations are more transparent than normal 
ones, sometimes showing a faint greenish hue in the centre of the swelling, 
and when opened they are found to be packed with the thread forms and 
granules in varying proportions (Plate II, fig. 8). In sections such cells have 
a bird’s nest appearance owing to the intertwining of the long bacterial 
1 The process of fertilization in the bed bug differs very remarkably from that usual among 
insects. The penis is inserted into an opening in the right side of the ventral plate of the fourth 
abdominal segment of the female. Immediately above this opening lies a spherical organ con¬ 
sisting of a mass of cells known as the organ of Berlese. This organ has no duct or outlet and the 
spermatozoa penetrate through the mass of cells composing the organ into the body cavity, 
finding their way to the oviducts and fertilizing the eggs in situ. The development of the embryo 
is frequently well advanced before the egg is laid. (For further details see Craig (1915), Indian 
Journal of Medical Research, n. No. 3, pp. 698-705.) 
