46 



caterpillar, grub or maggot. The general rule is to confine the term 

 " caterpillar " to the larvje of butterflies, moths, and sawflies, grub 

 to the larvae of beetles, and " maggot " to the larvae of flies. 



The three segments behind the head correspond to the thorax 

 of the perfect insect or imago, and, if any legs are present, a pair is 

 borne on each of these segments. 



Legs are also often present on the posterior segments ; these are 

 known as prolegs ; they are not jointed, and have fringes of bristles 

 instead of claws. 



There are mainly five pairs of these prolegs on the larvae of 

 butterflies and moths, and eight pairs on sawflies' larvae. 



The head and fourth body segment never bear any kind of legs. 



A larva, such as a caterpillar, possesses a head and twelve other 



segments. It is difficult sometimes even for experts to know to 



what insect the larva belongs on account of the moultings, as it 



usually moults five times in its existence as a larva. 



It is at this stage when the pest is worst, as the larva eats 

 enormously and is therefore most destructive. 



Food assimilates quickly to be stored away for the pupal stage ; the 

 caterpillar or larva also quickly grows, and, as the chitinous covering 

 will not stretch much, the larva bursts it and so moults. The next 

 stage is the pupal or chrysalis stage, where the insect takes* in no food, 

 but lives entirely on a store of fat accumulated during the larval 

 stage. 



In due time the membrane or case containing the pupa cracks, 

 and the imago or perfect insect creeps out to lay its eggs and reproduce 

 its species like its predecessor. 



When insects undergo the above changes, they are known to be 

 metamorphic, and insects belonging to the Coleoptera, Diptera, 

 Hymenoptera, Neuroptera, and Lepidoptera undergo these changes. 



Where, however, it is difficult or impossible to see these changes, 

 the insects are known to be ametamorphic, and this is the case in 

 the Kemiptera and Orthoptera. 



The fact that insects are produced from parents renders it of the 

 utmost importance, when dealing with injurious species, to become 

 acquainted with the habits of the females as well as of the larvae, 

 which latter are the destructive agents, and are the more generally 

 observed by gardeners, who can, by watching the life histories of these 

 insects, destroy them in greater proportion. 



The larvae, during their rapid growth, are more destructive to 

 vegetation than are the perfect insects, but among the groups provided 

 with a. mouth suitable for chewing, as the Orthoptera. or for puncturing 

 the tissues of plants and sucking their juices, as the Rhynchota, 

 particularly the Aphides, the perfect insects may be also as destructive 

 as the larvae. 



The insects provided with " biting " mouths are generally hardy 

 and mvulnerable. and are not injured by a wash quite strong enough 

 * Except m the case of those insects which have active " pupae."— F. J. C. 



