GARDEN PESTS IN NEW ZEALAND 



feed on the nutrient sap of plants, just in the same way as mosquitoes 

 do on blood, are modified for puncturing the tissues of plants; in such 

 insects the upper 1 lip is short, and both pairs of palps are atrophied, 

 but the jaws and accessory jaws are greatly lengthened in the form of 

 bristle-like stylets, which lie in a groove along the equally lengthened 

 lower lip (Fig. 3). The manner in which insects feed is orf great 

 importance in controlling them with insecticides, and the two types to 

 bear in mind are those that chew their food and those that suck the 

 feap of plants, reached by puncturing the tissues. 



As already stated, the thorax consists of the three segments imme- 

 diately behind the head, and carries the organs of locomotion ; its three 

 segments are distinct, and may be referred to, respectively, as the fore, 

 middle, and hind thorax. The cuticle of each thoracic segment consists 

 of a number of chitinised plates connected by membranous areas; these 

 plates are arranged in three series the baclq or dorsal; the lower or 

 ventral, forming the sternum; and the lateral, or side-pieces, connecting 

 the dorsal and ventral ones. 



At the lower surface of each thoracic segment is attached a pair 

 of legs, the members of each pair being separated by the sternum of 

 the segment to which they belong. The presence of three pairs of legs 

 is a character by which insects can be distinguished from all other 

 animals; indeed, on account of this feature, insects are sometimes called 

 the hexapods, or six-legged animals. Each leg is covered by a continua- 

 tion of the bod} r cuticle, and is five-jointed; the first two joints at the 

 attachment to the body are small ; the next two are long, and form the 

 greater part of the limb; while the fifth, or foot, consists of a varying 

 number of small joints, the terminal one bearing a pair of claws. 



In the typical winged insects there are two pairs of wings: one 

 pair attached to the middle thorax, and the other to the hind thorax; 

 owing to the development of muscles controlling flight, the middle and 

 hind thorax of winged insects are usually better developed than the fore 

 thorax; this is especially noticeable in the thorax of two- winged flies 

 (daddy-long-legs and blow-flies), where the hind wings are reduced to 

 vestiges, the power of flight being thus confined to the middle thorax, 

 which forms by far the greater portion of the whole thorax. 



Each wing, arising from the junction of the dorsal and lateral 

 thoracic plates, is a bag-like extension of the cuticle, flattened leaf-like, 

 so as to form a double flexible membrane. The wing membrane is 

 supported by several ribs or veins, which may be very numerous (grass- 

 hopper) or few (aphid), while the fore edge, where it cuts the air in 

 flight, is bordered by a stouter vein, ensuring rigidity. The fore and 

 hind wings of some insects work independently, but in agreement of 

 movement, while in others the fore and hind wings of each side are 

 coupled along their adjoining margins, giving greater rigidity during 

 flight. 



The abdomen of insects consists of a varying number of visible 

 segments ; each segment is covered by an upper and lower chitinous 

 plate connected by membrane, there being no side plates as are found 

 in the thorax. There are no organs) of locomotion (except in a very 



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