64 REPORT ON INJURIOUS INSECTS FOR 1904. 



only, making a total of ten. The caterpillars of a few moths are 

 footless. 



The larvae of Beetles possess a well-defined head and biting 

 jaws, and a pair of jointed legs on the first three segments behind 

 the head (Rose Chafer) or legs are entirely absent (Garden Weevil). 



The larvae of Flies (Diptera) are generally legless and usually 

 the head is merged into the thorax, some, however, possess 

 pseudopods and a head. 



* Those of the Hymenoptera (e.g., sawflies, wood wasps, etc.) 

 have six, eighteen or twenty-two appendages, and in sawfly 

 larvae the second abdominal segment always has a pair of pseudo- 

 pods, in some cases (wood wasps) the limbs are vestigial, while 

 in other cases they are absent. 



The larval stage is usually the one in which the insect does 

 the greatest amount of damage ; they feed voraciously, the daily 

 consumption of food often exceeding many times the weight 

 of the larva. With a plentiful supply of food they rapidly 

 increase in size, and as the chitinous skin is only capable of a 

 limited expansion it ultimately splits, and the larva comes out 

 with a new, and sometimes differently-coloured skin. This 

 process known as moulting usually takes place five times, but the 

 number is variable 2, 3, 4, 5, 7, 10, n, 12, and even 10, 25 and 

 30 moults are known in different insects. The larva is now said 

 to be full-fed and it changes to a pupa or chrysalis. 



The duration of the larval period is subject to much variation, 

 sometimes it is only a few days, while in other cases it may last 

 for months or even years. 



The Pupa. The full-fed larva generally either buries itself 

 in the ground (Rose Chafer) forming a cell of earthy particles, 

 or spins a silky cocoon (Codling Moth) in which it changes to the 

 pupal condition. After a time the pupal case containing the 

 insect cracks or splits, and the perfect insect or imago creeps out. 



The Imago. This is the fully-formed insect and may be 

 described as an animal consisting of thirteen segments, breathing 

 by tracheal tubes, with a single pair of feelers, and having the 

 body divided up into three distinct regions, head, thorax, and 

 abdomen, the three segments of the thorax each carrying a pair 

 of jointed legs. 



On reaching the imago stage, the pairing of the sexes is soon 

 effected, the female then lays her eggs and shortly afterwards dies, 

 the generation or life-cycle being thus completed. In some cases 

 the perfect insect only lives a few hours or days, but in others they 

 hybernate during the winter, and lay their eggs in the following 

 spring. 



Before the depredations of any particular species of insect 

 can be effectively dealt with, it is important that all the stages 

 and variations of the life-cycle should be clearly and thoroughly 

 understood. 



\ 8 R A 



OFTHK 



UNIVERSITY 



OF 



