INTRODUCTION. 3 



alists differ slightly in their arrangement ; but it may be said that 

 insects constitute a siibdivision of the animal kingdom known as 

 Arthropoda, which are characterised by having jointed limbs, and, 

 as a rule, a distinctly divided body. 



They rise in an ascending series in the following order — ^viz. : 



ARTHROPODA (4 classes). 



1. Crustacea . . Cmhs, Lobsters, ^-c. 



2. Arachnida . . Mites, Scorpions, Spiders. 



3. ]\Iyriapoda . . Centipedes and Millepedes. 



4. Insecta . . . Insects. 



In answer to the question, What is an insect % the general definition, 

 with some common exceptions, is that an insect is a creature whose 

 body is divided into three parts, has two antennae, six legs, and, as 

 a rule, passes through four stages of metamorphosis. 



Accepting this general definition, it may be said that the creatures 

 which, in point of anatomical structure and economic injuries, approach 

 nearest to insects, are mites and spiders ; and as a rough-and-ready 

 classification, it may be said that a mite is a creature whose body 

 is of one piece, a spider two pieces, and an insect three. 



The mites most injurious to vegetation are the Eriophyidse 

 (Phytoptidae), or four-footed mites. Spiders do not affect trees 

 directly, and therefore need not be considered. We find a certain 

 species of red-spider ^ injurious to the foliage of ivy and other plants, 

 sucking the juices from the leaves, and causing them to assume a sere 

 appearance. 



The whole class of Insects is divided into seven general or 

 principal orders — viz., Coleoptera (beetles) ; Orthoptera (earwigs, 

 crickets, grasshoppers, and locusts) ; Neuroptera (dragon -flies) ; 

 Hymenoptera (ants, bees, and saw-flies) ; Lepidoptera (butterflies 

 and moths) ; the Hemiptera, including the various species of bugs ; 

 and DiPTERA (two-winged flies). 



The Hemiptera is subdivided into two principal divisions — viz., 

 Hemiptera-Heteroptera, including the bugs ; and Hemiptera-Homop- 

 tera, including Aphidse or plant-lice, Cicadas, Psyllidse, and Coccidse 

 or scale-insects. 



1 The so-called "red-spider" — the dreaded enemy of the gardener — is only 

 a species of mite. 



