14 SCIENCE AND FRUIT GROWING 



Those insects which have a quiescent pupal stage, for the 

 conversion of the caterpillar, maggot or grub into the adult form, 

 are said to undergo a "complete metamorphosis": beetles, 

 sawflies and flies undergo such a change, as well as moths. 

 Aphides, scale-insects, leaf-hoppers and bugs undergo what is 

 called an " incomplete metamorphosis," wherein the changes 

 between the larva and adult are gradual, the insect in the pupal 

 stage resembling that in the larval stage, except that " wing- 

 buds " appear, these giving place at the next moult to fully 

 developed wings, and the insect then becoming perfect. During 

 the pupal stage in this case, the insect is active, and feeds through- 

 out it, and these insects, therefore, are injurious all their lives. 

 In the other cases, where the pupa is quiescent, damage is done 

 during the larval and adult stages (beetles), or during the larval 

 stage only (moths and sawflies). 



True caterpillars have a pair of jointed legs on each of the 

 first three segments of their bodies; the fourth and fifth seg- 

 ments have no legs, and on the next four segments, as well as 

 on the last, or anal, segment, there are pairs of soft pro-legs, or 

 sucker feet. In the case of " looper-caterpillars," this arrange- 

 ment is modified, there being only one pair of pro-legs in addition 

 to the anal pair, and these are on the ninth segment. False 

 caterpillars, as the larvae of sawflies are called, have always more 

 than four pairs of pro-legs. 



With moths and butterflies, the insect can rarely be attacked 

 when in the perfect state ; it must be dealt with, either in the 

 winter, by destroying the eggs and chrysalids, or in summer, 

 by destroying the larvae. In the former case, a strong insecticide 

 can be used, for the trees are then devoid of foliage, and the 

 substances selected should have, if possible, the twofold property 

 of not only destroying the eggs, etc., but of removing moss, 

 lichen and dead bark from the trees, thus reducing the number 

 of lurking-places available for harbouring insects and their eggs : 

 indeed, this is often the chief way in which winter washes are 

 beneficial; for insect eggs are generally so resistant, or so well 

 protected, that they cannot be destroyed by such washes without 

 injuring the trees. For cleansing properties in a winter wash, 

 we rely mainly on caustic substances, such as caustic soda or 

 caustic lime, but the destructive action may often be enhanced 

 by the addition of some other substances, notably paraffin oil. 



For summer treatment, a much weaker insecticide must be 

 used, or the foliage of the tree will be injured. With moths 

 the damage being done by the insect when in the caterpillar or 



