CHAP, xiv.] Insect Enemies 309 



no complex structure of the head are called maggots or strigs. 

 Several changes of skin take place in the larva before it enters 

 into the pupal state of rest. In the case of beetles (Coleoptera) 

 the structure and different sections of the mature insect are 

 externally distinguishable ; whilst in moths and butterflies 

 (Lepidoptera^ they are masked or indistinct. The pupa is some- 

 times to be found lying unprotected on the soil, under moss, 

 in fissures or under scales of the bark, and at other times it is 

 covered by a woven cocoon, often of large size, as in the case of 

 some of the Bombycidae; whilst with flies (Diptera), in place of 

 any cocoon, the last larval skin forms a protective case. The 

 stage of development which lasts longest is that in which the 

 insect hibernates. This is usually the larval stage, although 

 many injurious beetles hibernate as imagines. Except in 

 genera which hibernate either as ovum or pupa, these two 

 stages usually last only from two to four weeks. Thus the 

 devastating Spruce moth (Liparis monacha] appears after two 

 to three weeks' rest; whilst the destructive Pine moth (Gastro- 

 pacha pini} remains as a chrysalis for six to eight months from 

 autumn till spring, and the cockchafer (Melolonthd) even so long 

 as for four years. According to the Morphology ', or structure of 

 the Imago or mature insect, it is classified among the beetles 

 (Coleoptera], butterflies or moths (Lepidopterd], hymenopters 

 (Hymenopterd), flies (Dipterd), neuropters (Neuropterd], hemip- 

 ters (Hemiptera\ and orthopters (Orthoptera}. 



As soon as the imagines appear, they begin to swarm and 

 reproduce themselves. The male generally dies soon after 

 having entered in copula, although this is not the case with 

 beetles, which very often hibernate as imagines, nor with bees, 

 which live for four to five years. 



The complete cycle from ovum to ovum is termed the 

 Generation of any insect; this varies greatly in different 

 genera and species. Thus it is said to be multiple or manifold 

 as in the case of plant-lice (Aphides], and ichneumon-flies 

 (Ichneumonidae), of which several generations are produced 



