SPECIAL PROBLEMS OF INSECT CONTROL 153 



Of the nineteen orders the seven most important are : 



I. Diptera (di-, "two"; pteron, "wing"). Two membranous wings, 

 mouth parts for piercing and sucking or for lapping ; metamor- 

 phosis complete, larvse various in form and habit but always foot- 

 less; maggots, wrigglers, etc. Examples: flies, mosquitoes, gnats ; 

 40,000 known species ; estimated number, 350,000 (Howard). 

 II. Coleoptera (koleos, "sheath"; pteron, "wing"). Four wings, the 

 front pair horny cases which cover the membranous hind wings ; 

 mouth parts for biting ; metamorphosis complete, the larva a 

 grub, with usually six legs. Examples : beetles, potato beetle, 

 June beetle, lady beetle ; 100,000 known species (Galloway). 



III. Hemiptera(hemi-,"hali"', pteron, "wing"). Fore wings membra- 



nous, parchment-like or with horny bases and membranous tips ; 

 hind wings membranous ; many wingless forms ; metamorphosis 

 incomplete, the young resembling the adults, but wingless 

 the true " bugs." Examples : plant lice, scale insects, cicadas, lice, 

 water bugs; 20,000 known species; probably 80,000 in all 

 (Howard). 



IV. Orthoptera (orthos, " straight"; pteron, " wing "). Fore wings parch- 



ment-like, net-veined, hind wings almost always membranous; 

 mouth parts for biting ; metamorphosis incomplete, the young 

 resembling the adult, but wingless. Examples : grasshoppers, 

 crickets, cockroaches, walking sticks ; estimated more than 

 10,000 species. 



V. Lepidoptera (lepis, "scale"; pteron, "wing"). Wings and body 

 scale-clad ; mouth parts modified into a coiling, sucking tube, or 

 absent ; metamorphosis complete, larva a caterpillar. Examples : 

 butterflies and moths; 25,000 known species ((ialloway). 

 \\.Hymenoptera (hymen, "membrane"; pteron, "wing"). Wings 

 four, membranous, a few wingless forms ; mouth parts for 

 biting and lapping ; metamorphosis complete, larva maggot- 

 like. Examples : bees, ants, wasps, sawflies, ichneumons ; about 

 30,000 known species ; estimated number, 300,000 (Howard). 

 VII. Neuroptera (neuron, "sinew" ; pteron, "wing"). Wings four, mem- 

 branous, usually net-veined ; mouth parts for biting ; metamor- 

 phosis incomplete or complete ; larva usually unlike adult, 

 sometimes aquatic. Examples : dragon flies, lacewings, etc. 1 



1 This group is now subdivided into eight orders, among them the caddis 

 flies (Trichoptera), dragon flies (Odonata), and white ants (Isoptera). 



