28 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



..roG. 



style called a palpus or feeler. At each side of the lower lip is 



another palpus, these palpi being 

 sensory organs. 



Sucking Mouth-parts. In the 

 sucking insects these mouth-parts 

 are prolonged into a tube through 

 which the juices of the food plant 

 or animal arc sucked. In the 

 plant-lice and other bugs the lower 

 lip is elongated so that it forms a 

 tube, and the maxillae and man- 

 dibles consist of long hair-like 

 bristles, or setae, enclosed within 

 this tube (Fig. 20). The tip of this 

 beak is rested upon the surface of a 

 leaf into which the setae are thrust, 

 lacerating the tissue, and by a 

 pumping process of the mouth the 

 juices are sucked up through the 

 beak. The structure of the mouth- 

 parts of the various orders of suck- 

 ing insects varies considerably, but 

 all agree in that they suck up the 

 food in a liquid state. Any appli- 

 cation of a poisonous spray to the 



surface of foliage will be of no avail 

 FIG. 19. Cicada, showing mouth- 

 parts of a bug, a sucking insect: against them, though sure death to 

 a, seen from below, beak or most biting insects which chew the 

 rostrum (ro. G.) reposing be- . 



tween forelegs; b, head removed : leaves, bucking insects must there- 

 e, eye; Ibr., labrum; md., man- fore be killed by other means, 

 dible-setae; mx., maxillary setae; 

 lab., labium. 



How Insects Breathe 



Along the side of a caterpillar or larva, on one thoracic seg- 

 ment and on each abdominal segment except the last, is a small 

 oval spot, in the centre of which is a slit closed by two mem- 



