GENERAL CONSIDERATIONS 



3 



represented by a pair of knobbed appendages known as poisers. 

 The wings are variously modified for different uses. In the 

 Ix'etles the front pair are very hard and horny and not suited 

 for flight, but fitting closely together serve as a protection 

 to the hind wings which in repose are folded under them 

 (Fig. 1). 



The abdomen consists of from ten to twelve segments. In 

 many species the 

 tip in the female 

 is provided with a 

 sharp lancelike or 

 saw-edged oviposi- 

 tor, with which she 

 punctures the tissue 

 of plants and in- 

 serts her eggs in the 

 wound so made (see 

 Fig. 317, p. 358). 



How insects feed. 



The mouth parts 

 of insects are 

 adapted for feeding 

 on all sorts of tissue, from the tender leaves and ripening fruit 

 to the solid wood itself. From the standpoint of control it is of 

 great importance to know just how each insect obtains its food. 



For the purpose of control insects may be roughly divided 

 into three classes as follows : 



1. Chewing insects: Beetles and caterpillars belong here. 

 They are provided with hard horny jaws or mandibles with 

 which they bite off and swallow portions of the tissue of plants 

 as shown in Figure 2. It is usually possible to kill such insects 

 by poisoning their food with an arsenical. 



2. Sucking insects: Plant lice and other true bugs are 

 furnished with a beak containing four bristles united into a 



Fig. 2. — A caterpillar feeding, showing the biting 

 type of mouth parts. 



