GARDEN PESTS IN NEW ZEALAND 



the common cicada (wrongly called a locust), a change in both structure 

 and habit occurs during the life-cycle, the immature stages being adapted 

 to a subterranean life, while the winged adult frequents the foliage of 

 trees; all stages agree, however, in puncturing plant tissues with their 

 proboscis and sucking up the nutrient juices from the roots by the larva 

 and from the stems and leaves by the adult. 



The female cicada (Fig. 4) lays its eggs in colonies beneath the 

 young bark of trees and shrubs; the larvae, on hatching, drop to the 

 ground, into which they burrow ; the antennae and soft body are com- 

 paratively long, while the fore legs are greatly modified for grasping- 

 plant roots and as digging tools. After a number of moults, the body 

 shortens, the antennas come to resemble those of the adult, and the 

 rudiments of the wings appear. Growth and the activities of the 

 developing insect continue until finally the larva constructs an earthen 

 underground chamber, in which it lies torpid until ready to undergo the 

 final moult; in this inactive state, though still resembling the later 

 larval stages, the insect corresponds to the pupa of the moth. For the 

 final moult the pupa leaves the ground, crawls up some support (a tree 

 trunk or post), where the winged adult emerges, leaving the empty 

 pupal husk attached to the support. Besides the change in habit and 

 the possession of functional wings, the adult cicada differs in many 

 structural features from the immature stages. Outstanding differences 

 are the normal fore legs, the development of a "voice-box" in the male, 

 and an ovipositor in the female. 



An insect that shows some linkage between those having a true 

 metamorphosis and those having a partial metamorphosis is the aphis-lion 

 (Micromus tasmcwice), though undergoing a true metamorphosis itself. 

 The larvae are predaceous and feed upon aphids (Fig. 4). Its larva, 

 pupa, and adult are distinct forms, as in the moth, but the larva is not 

 of the specialised caterpillar or grub type, rather resembling in general 

 appearance the silverfish, or the type of young larva peculiar to such 

 insects as the earwig or thrips before the wing rudiments develop. 

 Furthermore, the pupa, though one in the strict sense, is capable of great 

 freedom of movement, its head, mouth-parts, antennae, legs and wings, 

 ensheathed by the cuticle, being freely movable, and not rigidly attached 

 to the body. 



A review of the early larval stages of the earwig, thrips and cicada, 

 prior to wing development, and of the aphis-lion larva, shows a con- 

 formity to a generalised type exemplified by the primitive silverfish. On 

 the other hand, the moth caterpillar exhibits another larval type more 

 highly specialised, though still retaining a modified semblance to the 

 silverfish type, while specialisation is carried to the highest degree in 

 the blowfly maggot, where all outward sign of the primitive larval type 

 is lost, Regarding the pupae, there are three types; the most simple i^ 

 the free pupa, like that of the aphislion, and some moths, beetles, etc., 

 where the appendages are freely movable. The most complex is the pupa 

 of the blowfly, enclosed in its puparium, while intermediate between 

 these two extremes are many moth pupae that have the appendages firmly 

 attached to the body, but nevertheless visible. 



