328 BIOLOGY: GENEKAL AND MEDICAL 



Arthrostraca. Of these the Amphipoda 

 present a few forms Cyamus that are 

 parasites of whales, and of the Isopoda, 

 many forms that are parasitic upon the 

 gills or scales of fishes. 



Class Hexapoda Insects. Of parasitic in- 

 sects there seems to be no end, nearly every 

 order appearing to be represented in some form 

 of injurious symbiosis with other insects or 

 upon other animals or plants. 



Order Mallophoga. All of the insects of this 

 order are parasitic upon birds and mammals, 

 the symbiosis being conjunctive. They in 

 general resemble lice, are without wings, have 

 biting mouth-parts, not fitted for sucking 

 blood, and live by eating the feathers and hairs. 

 Five species belonging to three genera are 

 known to infest the barnyard fowl. Other 

 species infest other birds. Certain species 

 sometimes, but rarely, infest the dog and cat. 

 Order Hemiptera. This order includes the 

 "bugs" and true lice, the plant lice and the 

 scale insects. The mouth-parts of the entire 

 group are fitted for piercing and sucking. 

 Most of them live by sucking vegetable juices; 

 some are predatory and seize upon other insects, 

 sucking their blood; some, like the lice and bed- 

 bugs, suck the blood of warm-blooded animals. 

 The scale insects, red-bugs, and plant lice do 

 great damage to crops. 



Order Lepidoptera. This order which com- 

 prises the butterflies and moths includes a great 

 number of representatives that are parasitic 

 upon plants in the larval state. One is a 

 parasite of bees' nests, devouring the wax and 

 so ruining the combs. The family Epiphy- 

 ropidse have larvae that live upon the backs of 



