370 



BIOLOGY OF THE LABORATORY MOUSE 



Arthropods 



Lice 



Several different species of lice have been reported as being found on the 

 house mouse. However, the most common louse of the laboratory mouse is 



probably Polyplax serrata (Burmeister) (Fig. 

 148), recently redescribed by Jancke (23). 

 Specimens taken from the mice at the Jackson 

 Memorial Laboratory have been identified as 

 this species by Dr. H. E. Ewing, U.S. Bureau 

 of Entomology and Plant Quarantine. P. 

 serrata is a common parasite of the house mouse 

 in Europe, but has been found only on laboratory 

 mice in this country (14). Hoplo pleura 

 lies per omydis (Osborn, 1891) has been reported 

 from the house mouse in California, and H. 

 acanthopus (Burmeister) occurs on the house 

 mouse in Europe (38, 15). The common species 

 of the rat is Polyplax spimdosa (Burmeister) 

 which is cosmopolitan in its distribution (5). 



Lice are permanent ectoparasites. They 

 move slowly and usually pass from one animal 

 to another only when the animals are in contact 

 with each other. Those found on the mouse are 

 of the type with sucking mouthparts, and feed 

 by piercing the skin and sucking the blood of 

 the host. The eggs are elongate and are 

 fastened to the hairs of the host most commonly 

 on the dorsal neck region or on the belly. 

 They can be seen readily by parting the hair, 

 and they afford one of the easiest ways of discovering an infestation. The 

 young are similar to the adults in structure, but are paler in color. After 

 several molts they reach the mature state. Under laboratory conditions 

 with the temperature controlled there is no interruption in their activity, 

 and many generations can be produced each year. 



Mice infested with lice usually display a general unhealthy appearance. 

 This is somewhat due to the loss of blood, but probably more to the irritation 

 which the parasites cause making the animals restless and constantly 

 scratching. 



Fig. 148. — Polyplax ser- 

 rata, adult female. Dorsal 

 view (X75). 



