60 THE SCOLYTID BEETLES. 



FIFTH GENERATION. 



There may be a partial or beginning of a fifth generation, especially 

 at the lower elevations and more southern localities of the northern 

 section, the individuals of which pass the winter as parent adults 

 and young larvae. 



It is evident that in the northern .section of the range of this spe- 

 cies there are from two to three complete seasonal generations dur- 

 ing the period from about the first of May until activity ceases in 

 the fall, or at any rate all of the broods of at least two generations 

 develop and emerge during the period of activity within the range 

 including the higher elevations of North Carolina and lower eleva- 

 tions at the northern limit, and that all of the broods of at least 

 three generations develop and emerge at the medium and lower ele- 

 vations south of Virginia, represented by a central locality included 

 in a range of, say, 1,000 feet above and 500 feet below Try on, N. C, 

 while portions of the fourth and all of the fifth generation overwinter. 



PERIODS OF DESTRUCTIVE ATTACK. 



In the area including the mountains of North Carolina and north- 

 ward there is one principal period of destructive attack, viz, during 

 August and September, and in the area represented by Tryon, N. C, 

 there are two principal periods of destructive attack, one from the 

 middle of July to the last of August, the other during September and 

 October. 



Southern Section. 



In the southern section, including the Atlantic or Gulf region of 

 loblolly and longleaf pines, there is a complex overlapping of prob- 

 ably five or six generations, most difficult to define on account of 

 the almost continuous activity during the year, but of course more 

 or less retarded during the colder weather of the winter months. It 

 would appear, however, that the principal periods of destructive 

 attack are similar to those of the Tryon section. 



HABITS. 



The adult beetles enter the living bark, usually on the upper por- 

 tion of the main trunk of standing healthy or injured trees or on the 

 entire trunk of newly felled ones, and excavate long, sublongitudinal, 

 winding egg galleries (figs. 19-22) through the inner bark. Eggs are 

 placed in little niches along the sides of these galleries at more or 

 less regular intervals of one-half inch or more. 



The freshly hatched larvae, which are short, stout, whitish grubs 

 with a faint frontal elevation in the middle of the head and with 

 the opposite end of the body blunt or truncate, excavate their larval 

 mines at right angles to the egg gallery (fig. 19), and usually exposed 



