88 
Parasitic Arthropods 
The peculiar disagreeable odor of the adult bed-bug is due to the 
secretion of the stink glands which lie on the inner surface of the 
mesostemum and open by a pair of orifices in front of the metacoxae, 
near the middle line. In the nymphs, the thoracic glands are not 
developed but in the abdomen there are to be found three unpaired 
dorsal stink glands, which persist until the fifth molt, when they 
become atrophied and replaced by the thoracic glands. The nymphal 
glands occupy the median dorsal portion of the abdomen, opening 
by paired pores at the anterior margin of the fourth, fifth and sixth 
segments. The secretion is a clear, oily, volatile fluid, strongly acid 
in reaction. Similar glands are to be found in most of the Hemiptera- 
Heteroptera and their secretion is doubtless protective, through 
being disagreeable to the birds. In the bed-bug, as Marlatt points 
out, “it is probably an illustration of a very common phenomenon 
among animals, i. e., the persistence of a characteristic which is no 
longer of any special value to the possessor.’’ In fact, its possession 
is a distinct disadvantage to the bed-bug, as the odor frequently 
reveals the presence of the bugs, before they are seen. 
The eggs of the bed-bug (fig. 70) are pearly white, oval in out¬ 
line, about a millimeter long, and possess a small operculum or cap 
at one end, which is pushed off when the young hatches. They are 
laid intermittently, for a long period, in cracks and crevices of beds 
and furniture, under seams of mattresses, under loose wall paper, 
and similar places of concealment of the adult bugs. Girault (1905) 
observed a well-fed female deposit one hundred and eleven eggs 
during the sixty-one days that she was kept in captivity. She had 
apparently deposited some of her eggs before being captured. 
The eggs hatch in six to ten days, the newly emerged nymphs 
being about 1.5 mm. in length and of a pale yellowish white color. 
They grow slowly, molting five times. At the last molt the mesa- 
thoracic wing pads appear, characteristic of the adult. The total 
length of the nymphal stage varies greatly, depending upon condi¬ 
tions of food supply, temperature and possibly other factors. Mar¬ 
latt (1907) found under most favorable conditions a period averaging 
eight days between molting which, added to an equal egg period, 
gave a total of about seven weeks from egg to adult insect. Girault 
(1912) found the postembryonic period as low as twenty-nine days 
and as high as seventy days under apparently similar and normal 
conditions of food supply. Under optimum and normal conditions 
of food supply, beginning August 27, the average nymphal life was 
