1 88 ARTHROPODA 



monarch butterfly and is supposed to be thus protected. (Natural 

 Selection, p. 515.) The swallow-tailed butterflies (Papilionidae) 

 include the black swallow tail whose larvae feed on celery and parsley; 

 and the tiger swallow tail^ yellow in color, which is the largest common 

 species. Caterpillars of the cabbage butterflies devour the outer 

 leaves, then bore to the heart of the cabbage. 



The alfalfa caterpillar {Ewymus) attacks alfalfa in the West. 

 The gossamer winged butterflies {Lycaenidae) are the smallest and 

 most delicate butterflies. The larvae are small and slug-like and 

 feed on plants. One carnivorous form, the " harvester," is valuable 

 to the fruit-grower since its larva feeds on the wooly aphids. 



Pigment in Butterfly Wings. — One of the present day fads is that 

 of enclosing butterfly wings in glass brooches. The natural color 

 should remain for some time since colors in the wings of fossil but- 

 terflies were found persistent when exhumed by Dr. R. J. Tillyard 

 millions of years after they were sealed with mud. Exposure to the 

 air caused rapid fading, however. 



Order 16. Diptera. {Flies, Mosquitos, etc.) — The Diptera, as 

 the name indicates, have two wings. They have sucking mouth 

 parts, and the metamorphosis is complete. There are over 7,000 

 species of Diptera in North America. 



The common housefly {Musca domesticd) carries typhoid, tubercu- 

 losis and other bacterial diseases. It is also important in the 

 transmission of the eggs of several species of Nematode and Cestode 

 worms. A fly wing is said to vibrate 330 times per second. House- 

 flies lap up liquid food with their folding proboscis. 



The blow fly and th.& flesh fly {Sarcophagidae) deposit their eggs 

 on meat and cheese on which the maggots feed. The horse fly 

 {Tabanidae) attacks cattle and horses and even man. The female 

 feeds on blood, but the male lives on nectar. The tachina fly 

 {Tachinidae) is an important enemy of caterpillars (particularly 

 the army worm), and kills many locusts and leaf-eating beetles. 



The bot-flies {Oestridae) attack cattle and horses. The eggs of 

 the horse bot-fly, licked off their legs by infested animals, develop 

 in the lining of the stomach until the time of pupation when they 

 are extruded. 



The ox-warble larvae ( Hypoderma lineata) pass to the esophagus 

 of the host in the same manner as those of the horse bot-fly, but 

 then burrow into the subcutaneous tissue and lodge just under the 



