602 INSECT A ORDERS ANOPLURA AND DIPTERA. 



habits and transformations. They are small insects, but some are capable, 

 like the Phylloxera of the vine, of ruining or crippling a vast industry over a 

 considerable portion of the world. They exude a sweet liquid known as 

 honey-dew, of which ants are extremely fond ; and to ants they bear the re- 

 lation of milch-kine, and are frequently protected and tended by them 

 accordingly. In some cases the ants are even said to superintend the breeding 

 of the various broods. 



The Aleyrodidce are a small family, of which the perfect insects resemble 

 very small moths, covered with a whitish powder. One or two species are 

 very destructive to cabbages and tomatoes. 



The Coccidce, or scale-insects, differ much from all other insects. The male 

 has no rostrum, and only two wings, but possesses anal setae, and the wingless, 



short-legged female settles herself 

 Family permanently down on a leaf or twig, 



Coccidce. and forms a scale-like covering for 

 Scale-Insects, her own eggs. Some of these furnish 

 useful products, such as cochineal, 

 but others are highly injurious. One species, Icerya 

 purchasi (Maskell), caused great damage in California; 

 but by the advice of the late Prof. C. V. Riley, Fig.95.Aleyrodesproletdla, 

 an Australian lady-bird, Novius cardinalis (Muls.), Linn - Magnified, 



was introduced into the country, and has since been 



effectual in keeping the ravages of the Icerya within bounds. Many of the 

 Coccidce, especially the larval forms, are covered either with a white cottony 

 substance or with large plates of white wax, which in some cases has a com- 

 mercial value. 



ORDER ANOPLURA. 



The true lice, which are wingless insects, parasitic on mammals, and 

 furnished with a sucking proboscis, are sometimes regarded as a sub-order of 

 Hemiptera. Three species at least infest man in European countries, and, 

 besides the discomfort and annoyance which they occasion, are either the 

 cause of, or accompany various diseases. They multiply very rapidly, but 

 can usually be destroyed or kept away by ordinary attention to cleanliness. 

 In warm countries, or, indeed, in any community where cleanliness is neglected, 

 they are universally prevalent. There has been much controversy as to 

 whether the lice infesting different races of mankind are to be regarded as 

 distinct species, or only as slight varieties. Even the two species of lice 

 which infest the head and clothes respectively, Pediculus capitis (Linn.), and 

 P. vestimeuti (Nitsch), although certainly distinct, are so much alike that they 

 can hardly be distinguished from each other. The third species, the crab 

 louse, Pthirius inguinalis (Leech), belongs to a distinct genus, and is much 

 smaller, broader, and shorter than the others. 



ORDER DIPTERA (FLIES). 

 The Diptera, or Flies, differ from other insects in possessing only two wings 



