554 FAMILY SCOLYTIDAE 



November. In favourable years some of these latter de\elop into beetles, 

 which pass through the winter either in the pupal chamber, or, not 

 improbably if fully mature, in the thick bark of the trees. The remainder 

 of the larvae pass the winter at the end of their j^alleries, in which they 

 gnaw out a small chamber and then envelop themselves in a thin, papery 

 cocoon. Those which, as above described, go on to the beetle stage, are the 

 beetles of the fourth generation, and are the ones which appear in the 

 spring (April) and lay the eggs of the first generation of the year. The 

 hibernating larvae change early in the }'ear into pupae, and these into 

 beetles, the latter appearing also about the beginning of May, and this leads 

 to the generations o\erlapping to some extent. 



It is probable that when the circumstances of its environment are 

 unfavourable, such as damp, very cold weather, shady places at high 

 elevations, etc., the normal number of generations passed through during 

 the year is three. Similarly in xavy favourable situations, and in warm, dry 

 years, it is not improbable that the insect will be found to pass through 

 four complete life- cycles. 



The time when these various generations may be expected to appear in 

 the forest is therefore somewhat as follows : — 



Gknikation I. 



I".nd (if April .......... Eggs 



1st week in May to 1st week in June ..... Grubs 



1st week in June to 3rd week in Jime ..... Nymphs 



2nd week in June to end of June ...... IJeetles 



GKN KRAI ION 11. 



3rd week in June ......... Eggs 



4th week in June to 4ih week in July ..... Grubs 



4th week in July to middle of August ..... Nymphs 



1st week in August to 3rd week in August .... IJcctles 



Gkneration 111. 



2nd week in August ......... Eggs 



3rd week in August to 3rd week in .September . . . Grubs 



3rd week in September to 1st week in October . . . Nymphs 



End of September to middle of October ..... Hcetles 



Genfration 1\'. 

 1st week in October ......... Eggs 



2nd week in October to 2nd week in November . . . Grubs 



(.Some of these will hibernate and pass the winter as grubs.' 

 2nd week in November to end of Noveml^er .... Nymplu 



3ril week in November to beginning of following May . . ISectles 



This insect, both in the larval and beetle state, does serious injur}' to 



the blue pine and the spruce [Picca nwrinda). The 

 Damage Committed ^, .. iiiurj- i 



J r'. P 1 oiiiicua IS not usually to be lound m yoimg poles, 



though it may attack them near the base, and it does 



not attack \oung growth. In older poles it is often present, but it 



