INSECTS INJURIOUS TO VEGETABLES 



atives in order that we may be able to distinguish friends 

 from foes and true insects from related forms. It is, of 

 course, not essential that all of the Latin names which insects 

 bear should be memorized, nor that anything approaching a 

 complete classification be studied. The object of what is here 

 presented on this topic is to assist in the ready identification by 

 orders of such creatures as may come under observation as 

 enemies or suspected enemies to plants under cultivation. 



It is first desirable to eliminate animals which are not true 

 insects but are related to them. These are all included (with 

 true insects) under the branch 

 Arthropoda of the Animal King- 

 dom and are distinguished by 

 having their bodies composed of 

 rings or segments more or less 

 similar, joined together, most of 

 them bearing jointed legs, the last 

 character separating them from 

 earthworms, eel-worms, or hair- 

 worms, which have many segments 

 but no legs. This branch is di- 

 vided into four classes: 



Crustacea (Crabs, lobsters, 

 shrimps, crmvUsh, and soz^'-bngs 

 \^Oniscid(c'\). — Of this class only the sow-bugs or pill-bugs are 

 apt to be confused with insects, and are of some economic 

 importance, though not so injurious as many suppose. A 

 common injurious species is shown in figure 5. 



Arachnida {Scorpions, daddy long-legs, spiders, mites, etc.). — 

 The scorpions are well known in the South and need no de- 

 scription. The same is true of the daddy long-legs or harvest- 

 men, and spiders are everywhere. Among the mites, however, 

 we have one species, the so-called red spider, which is quite in- 

 jurious at times and which as it is commonly supposed to be 

 an insect we will treat in one of the following chapters. 



Fig. 5.— Water-cress sowbug {Man- 

 casellus brachyuvus). Enlarged. 

 (After Richardson) 



