FOREST PROTECTION 21 



erally, phytophagous insects found in the forests, are more or 

 less injxirious. The families which contain most of the injur- 

 ious species are — 



Order Coleoptera: Families Cerambycidce, Bu- 

 prestidce, Elateridce, Ptinidce, Scarabaeidce, ChrysO' 

 melidce, CurculionidcB, Brenthidoe, Scolytidce. 

 Order Lepidoptera: Families Arctiidce, Bomby- 

 cidce, Cossidce, Hesperidce, Liparidce, Noctuidae, Pa- 

 ■pHionidoe, Zygaenidce, 



Order Hymenoptera: Superfamilies Tenthredi- 

 noidea, Cynipoidea. 



Order Hemiptera: Families Cocddoe, Apkididoe, 

 Cicadidae. 



Order Diptera: Families Cecidomyiidce, Syrph- 

 idce. 



Order Orthoptera: Families Locustidce, Phaa- 

 midcE. 



III. Insects are divided into three groups, according to the rela- 

 tion that exists between the younger stages and the adults. 



a. The Ametabola, which includes a single order, the 

 Thysaneura, in which the yoimg and adults differ 

 only in size. 



6. The Hemimetabola, in which are included the Orthop- 

 tera, the Hemiptera, etc., etc. In this group the 

 young and adults differ not only in size, but in several 

 other characters, and the young become more and 

 more Uke the adults after each molt. 



c. The Metabola, in which are included the Coleoptera, 

 Lepidoptera, Hymenoptera, Diptera, etc., etc. In 

 this group, the young and the adults are totally im- 

 like, and before taking the mature form, the larvae go 

 through a resting stage. 



The first stage of the insect is the egg, and after hatch- 

 ing, it arrives at maturity through a series of molts. 

 On hatching, the young of the Metabola are called 

 larva (caterpillars, maggots, grubs); and in the Ameta^ 

 bola and Hemimetabola, they are called nymphs. There 

 are several molts during the larval or njTnphal stage, 

 and the period between any two of them is called an 

 instar. The quiescent stage during which the larvae 

 of the Metabola change to imagines, is called the pupa; 



