40 THE SIX-FOOTED INSECTS 



side a short distance from the margin of the compound eye, 

 and the third, if })resent, h)wer down on the face and on the 

 middle hne. 



The lower ]jortion of the face is di^■ided into cli/peus, 

 which forms the basis for attachment of the lahrum or upper 

 lip, the moval)le flap-like part which covers the front part 

 of the mouth. Beneath this are the strong mandibles 

 capable of cutting and tearing the leaves of plants, and in 

 some cases of inflicting a severe bite if handled. 



Next to these is a pair of more slender appendages, the 

 auxiliary jaws or the maxiUoe. These have a jointed structure 

 and bear each a slender, jointed appendage called the 

 tna.riUari/ palpus. 



Beneath the maxillae is the labium, which is in reality a 

 structiu-e formed by the fusion of a pair of organs similar 

 to the maxilla^ and sometimes termed the second maxillae. 

 The first part of this organ is called the inenium, and is 

 attached by the submentum to the gula or basal part of the 

 head. Attached to the mentum are the glossa and 2^«^o- 

 glosscp, at the sides of which are the labial jMlpi. 



The structure of the mouth is of special interest on account 

 of the relation to the food habits. It becomes possible to 

 determine from this structure what the food habits of any 

 particular insect may be. Where the mandibles and maxillse 

 are well (le\eloped and capable of biting and tearing the 

 foliage of plants, we may assume that the diet is herbivorous. 

 However, if the insect ca]:)tin'es and devours other insects 

 while the mandibles appear wanting or they seem to have 

 developed a suctorial tube fitted for puncturing the tissue 

 of plants and animals, a liquid diet may be assumed, and it 

 will follow that insects of this kind would not be affected 

 by poisons applied to the surface of the plants. We have 

 liere then a basis for the application of poisonous solutions 

 such as the arsenites, which are effective for those insects 

 which consume the surface of the leaf, or, on the other hand, 

 for the application of oil\- substances for those of suctorial 

 habits which enables them to secure the juices of plants 

 without consuming auA- of the siu-face. For insects of this 



