124 



FOREST ENTOMOLOGY. 



say from six to twelve years of age, is often rather risky, more 

 especially if followed by a dry summer. Under such circumstances 

 the bill of mortality is a heavy one, and the beetles are generally 

 found on the dead or most sickly trees. It is just possible that, 

 though the beetles are always found on dead or dying trees, they may 

 be the means of partially killing several trees of the pine tribe. 



It often happens that many transplanted Austrian pines hang, as 

 it were, for one season, that is to say, they make no growth, but 

 simply remain green. If there be no insect enemies, the trees will 

 recover the following year, but a severe beetle attack often kills what 



might otherwise recover. In the case of 

 Douglas firs, the brown foliage emphatically 

 declares the dead plants. 



Altum 1 relates that 100,000 seven-year-old 

 plants were killed in one season by this beetle. 

 In this country such an attack would be 

 considered primarily due to, and afterwards 

 accelerated by, the absence of healthy con- 

 ditions, that is to say, that the trees had 

 been planted at the wrong season of the year, 

 and on too dry a situation. 



With regard to the life-history of the in- 

 sect, I have found it in all its various stages 

 throughout the whole year, and am therefore persuaded that Eichhoff's 

 remarks regarding the respective broods are right viz. : 



" I. Spring swarm in May or June ; larvae in May, June, and July ; 

 pupse and imagines in July and August. 

 Summer swarm from July till October ; larvas in July, August 

 till October, and over winter ; pupa? and imagines in Sep- 

 tember or October till May. 

 Autumn swarm from August till October, larva? over winter, 

 imagines and swarms and broods in May and June." 2 

 The beetle (fig. 121) is from 2 to 3 mm. long, pitchy black in colour, 

 shiny, and covered with a very fine pubescence ; antennas and legs 

 ferruginous ; thorax constricted in front and punctured behind, and 

 it has a sort of pinched appearance. The elytra have distinctly 

 punctured rows. The male can be very easily distinguished by its 

 having a projecting hook on each elytron. 



1 Forstzoologie. 2 Die Europaischen Borkenkafer. 



Fig. 121. Pityogenes biden- 

 tatus. (From Fisher's 

 'Forest Protection.') 



II. 



III. 



