PHYLUM ARTHROPODA. INSECTS 



247 



sharp and pointed, being fitted for piercing 

 and sucking. Suctorial mouth parts are 

 adapted for piercing the tissues of plants or 

 animals and sucking juices. The mouth parts 

 of the honey bee are suctorial, but highly 

 modified. In the female mosquito (Fig. 

 146), the labrum and hypopharynx com- 



bined form a sucking tube; the mandibles 

 and maxillae are piercing organs; the hypo- 

 pharynx carries saliva; and the labium consti- 

 tutes a sheath in which the other mouth 

 parts lie when not in use. The proboscis of 

 the butterflies and moths is a sucking tube 

 formed by the maxillae (Fig. 145). 



Salivary duct 

 Esophagus 



Labi 



Figure 146. Mouth parts of a female mosquito showing the modifications adapting them for 

 piercing and sucking. The mouth parts which are shown in soHd black are those used in stinging. 



The mouth parts of insects are of con- 

 siderable importance from an economic 

 standpoint, since insects that eat solid food 

 can be destroyed by spraying the food with 

 poisonous mixtures, whereas those that suck 

 juices must be smothered with gases or 



killed by substances acting as direct contact 

 poisons. The newer insecticides known as 

 general purpose compounds are very effec- 

 tive for they act either as a stomach or a con- 

 tact poison, depending on the manner in 

 which the insect encounters them. 



