802 ANIMALS AND THEIR ENVIRONMENT 



ChicKe-n lotxse- Cattle lozise 



Figure 39.2. Mallophaga. Ventral views showing biting mandibles. Most species 

 infect birds and have two claws on each foot (left). The few that infect mammals 

 have single claws (right) resembling those of the Anoplura. (After Borror and DeLong.) 



362. Ectoparasites 



Parasites that feed at the surface of the host fall into three major 

 categories: those that eat dead material such as hair, feathers, flakes of 

 skin; those that suck blood; and those that feed on living tissue. 



Parasites Feeding on Dead Material. The largest group of ecto- 

 parasites that feed on dead surface material is an order of insects, the 

 Mallophaga (Fig. 39.2). These are known as bird lice, since most of them 

 are found on birds, or biting lice, because they have jaws for biting and 

 chewing. A few species are found on mammals. They do not directly 

 injure the host but the constant irritation of their presence as they feed 

 on feathers or fur can produce restlessness and insomnia with loss of 

 vigor and weight. A few of the species chew down into the shafts of the 

 feathers until they reach live tissues and draw blood. 



Bloodsuckers. The list of animals that suck blood but do not re- 

 main with the host between meals is long: leeches, mites, ticks, lice, 

 fleas, bedbugs, mosquitoes, sandflies, midges, blackflies, horseflies, tsetse 

 flies and vampire bats. The true parasites that remain with the host are a 

 much smaller group, including a few of the leeches, a few ticks and mites, 

 bedbugs, the sucking lice and fleas. The two major groups are the suck- 

 ing lice (order Anoplura) and the fleas (order Siphonaptera) in the class 

 Insecta. 



Sucking lice spend their entire life cycle on the same host and are 

 transferred to new host individuals through body contact or by migra- 

 tion from hosts that die. All of the species parasitize mammals. The 

 head louse, the body louse and the pubic louse or "crab" parasitize 

 man (Fig. 39.3). Fleas (Fig. 39.4) are free-living as larvae. The eggs are 

 dropped, usually in the nest or sleeping place of the host, where they 

 hatch into small worms that feed on debris. After pupation they emerge 

 as full-grown adults that seek the proper host. Although a few species 

 parasitize birds, most fleas are found on mammals. 



Bloodsuckers are not only harmful as parasites but are dangerous 

 as carriers of disease organisms. During the fourteenth century about 

 25 million people, one fourth of the population of Europe, died of 

 bubonic and pneumonic plague. This disease is caused by a bacterium 

 that can be carried in rats and other rodents where it is relatively 



