372 BIOLOGY OF THE LABORATORY MOUSE 



One can readily recognize fleas as such by their wingless, laterally com- 

 pressed bodies and their remarkable jumping ability. They feed entirely 

 from the blood of the host, but do not necessarily remain on the host all the 

 time for they are often found in the nest of the host or they may even be 

 found throughout the laboratory. The female lays her eggs in the nesting 

 material or among the hairs of the host. In the latter case the eggs usually 

 have dropped to the bedding of the host before they have hatched. The 

 worm-like larvae are not parasitic but feed on any organic material in the 

 debris in which they live. After remaining in the larval stage for a week or 

 ten days, during which time they molt three times, they pupate within silken 

 cocoons. Under conditions favorable for development such as would be 

 found in a laboratory, the adults emerge from the pupae after another period 

 of a week or ten days. 



Fleas irritate their hosts considerably, and danger in flea infestation also 

 lies in the possibility of their spreading disease among laboratory animals. 

 It is well known that fleas transmit bubonic plague and endemic typhus and 

 that they serve as the vector for the rat trypanosome and probably also that 

 of the mouse. Just how many more pathogenic organisms they transmit is 

 not known, but there are probably many. 



Regular weekly cleaning of the cages of laboratory mice automatically 

 controls flea infestations as such treatment destroys the developing larvae 

 and pupae. However, the source of flea infestations in buildings can some- 

 times be traced to a dog or a cat which frequents the building. In such 

 cases the infestation can be controlled by cleaning and disinfecting the bed 

 in which the dog or the cat sleeps. 



Bedbugs 



In some laboratories the bedbug, Cimex lectularius Linne, has adapted 

 itself to feeding on the experimental animals and has proved to be a very 

 disagreeable pest. With the ideal conditions presented by the laboratory 

 and with a constant, abundant supply of food, bedbugs grow vigorously and 

 breed rapidly. 



They are dark, flat insects with vestigial wings (Fig. 149). They feed 

 entirely on the blood of the host, being active at night and retiring for the 

 day to cracks and crevices in the cages and racks. Each female lays from 

 75 to 200 eggs which she conceals in the crevices where she hides. The 

 young bedbugs, or nymphs, are similar to the adults but are paler yellow in 

 color. They too feed on the blood of the host. After molting five times the 

 adult with the rudimentary wings appears. 



