16 



THE TYPES OF EGG-TUNNELS. 



The egg-tunnels present many variations in form, even in the same genus 

 and interesting similarities in habit occur between species belonging to widely 

 separated genera. Several arrangements for classifying the ipid egg-tunnels 

 have been suggested. The variations in the tunnels are so numerous that a 

 detailed classification must be cumbersome if at all complete, and the brief 

 arrangement in the following table will perhaps be more useful for the purpose 

 of this bulletin: 



IRREGULAR ELONGATE TUNNELS Dendroctonus, Hylurgops, Hylastes, etc. 



IRREGULAR SHORT TUNNELS. Dryoccetes (in part), etc. 



SIMPLE LONGITUDINAL TUNNELS. Phlceosinus, Eccoptogaster (in part), 



Chramesus, etc. 



SIMPLE TRANSVERSE TUNNELS. Cryphalus, Eccoptogaster (in part) ; rare. 

 FORKED TUNNELS.' Longitudinal or transverse; Leperisinus, Pseudo- 



hylesinus, Eccoptogaster (in part), Phthorophlceus, etc. 

 RADIATE TUNNELS. Ips, Pityogenes, Pityophthorus (in part), Polygraphus, 



etc. 



CAVE TUNNELS. Cryphalus (in part), Pityophthorus (in part). 

 PITH TUNNELS. Micracis, Stephanoderes, Pityophthorus (in part). 

 AMBROSIA TUNNELS. Simple; Anisandrus, Xyleborus. Compound; 

 Gnathotrichus, Pterocyclon, Trypodendron, Xyloterinus. Page 11. 



PLATE 3. 

 AMBROSIA-BEETLE TUNNELS. 



Fig. 1, Anisandrus populi Sw.; eggs, larvae and pupae; 1| times natural size.* 



Fig. 2, Trypodendron retusus Lee.; tunnel in poplar; about natural size, showing a pupa in its 



cradle. 



Fig. 3, Anisandrus obesus Lee.; tunnel in beech, showing eggs lying in the inner end.** 

 Fig. 4, Trypodendron retusus Lee.; larvae; about natural size.* 

 Fig. 5, Anisandrus pyri Peck; tunnels in apple; about | natural size.* 

 Fig. 6, Trypodendron retusus Lee.; tunnels in poplar; about natural size. 

 Fig. 7, Trypodendron betulce Sw.; tunnels in birch; \ natural size. 

 Fig. 8, Gnathotrichus materiarius Fitch; tunnels in pine, showing larvae, pupa, and adult; natural 



size.** 



Fig. 9, Anisandrus pyri Peck; exit holes in apple limb; about | natural size. 

 Fig. 10, Anisandrus populi Sw. ; tunnels in poplar. 



Fig. 11, Trypodendron retusus Lee.; tunnels in poplar, showing small larvae.* 

 Fig. 12, Eggs, larvae, and pupae of Anisandrus populi Sw.; slightly enlarged. 



PLATE; 4. 



BARK-BEETLE TUNNELS (ORIGINAL.) 



Fig. 1, Eccoptogaster subscaber Lee.,; tunnels in lowland fir; wood surface; natural size. 

 Fig. 2, Pseudopityophthorus minutissimus Zimm.; tunnels in hazel; wood surface; natural size. 

 Fig. 3, Dendroctonus monticolce Hopk.; pitch-tubes in western white pine trunk; much reduced. 

 Fig. 4, Orthotomicus ccelatus Eichh.; tunnels in white pine bark; about natural size. 

 Fig. 5, Pityophthorus nitidus Sw.; tunnels in pine twig, on the wood surface and in the pith; 



3 natural size. 



Fig. 6, Study-tunnels, covered with sheet celluloid. 



Fig. 7, Phthorophlceus picece Sw.; tunnels in white spruce branch; \ natural size. 

 Fig. 8, Orthotomicus caelatus Eichh.; tunnels in white pine, inner surface of bark, showing inner 



bark entirely reduced to powder. 

 Fig. 9, Dendroctonus borealis Hopk.; tunnels in white spruce, inner surface of the bark; (the 



right end of the figure should be uppermost, the (black) egg-tunnels vertical); the larvae 



feed in congress at first and finally separate to cut individual mines; much reduced. 

 Fig. 10, Ips perturbatus Eichh.; tunnels in white spruce bark; natural size. 

 Fig. 11, Eccoptogaster subscaber Lee.; tunnels just commenced in balsam; f natural size. 

 Figs. 12 and 13, Pityogenes hopkinsi Sw.; tunnels in white pine limb; $ natural size. 



* Original ** Author's illustration 



