78 ENTOMOLOGY. 



Although the Hemiptera are not so numerous in species 

 as the Coleoptera, Diptera, or Hymenoptera, they possibly 

 outnumber the Lepidoptera. Uhler states that about 

 27,000 species occur in museums, and that there are prob- 

 ably not less than 50,000 species now existing. The known 

 forms are distributed in very nearly the following propor- 

 tions: South America, 10,000; North America, 5000; Cen- 

 tral America and the West Indies, 2000; Europe, 3000; 

 Asia and its islands, 3000; Africa and its islands, 3000; and 

 Australia, New Zealand, and the Philippines, about 1000 

 species. 



Sub-order 1. Pediculina. The parasitic Hemiptera or 

 lice are wingless and have a beak-like sucker, which is soft 

 and retractile, with two protrusible chitinous bristles. The 

 feet are adapted for clinging to hairs, as they are hooked, 

 while the body is soft, and the thoracic segments are not 

 divided into separate pieces, as in other Hemiptera and 

 nearly all other insects. The eggs, called " nits'" (Fig. 30, 

 r), are oval and attached to hairs. All the species live on 

 mammals, none on birds. 



Though evidently allied to the wingless Cimex, and form- 

 ing a group standing near it, we have, as a matter of con- 

 venience, to place them at the bottom of the entire order in 

 a sub-order by themselves, interpolating the Homoptera 

 between them and the Heteropterous Hemiptera, to which 

 they more nearly belong. Parasitism has so degraded them 

 that the marks of relationship to their true ancestors have 

 been effaced. The lice may be said to be a downward-bent 

 twig of the Heteropterous branch, while the Homoptera 

 form the highest branch of the ordinal tree. 



Family Pediculidae. Pediculus capitis De Geer, the head-louse of 

 man; P. vestimenti Burm. (larger and paler); Phthirius pubis (Liiiu.), 

 the crab-louse. 



Sub-order 2. Homoptera. In Hemiptera of this group 

 the wings are somewhat opaque throughout, or transparent, 

 and lie roof-like over the body. The head is large, and the 

 beak appears to arise between the fore legs. Many of the 



