1919] Blackman — Notes on Forest Insects 87 



the males^ which leave their old host several days earlier than the 

 females of the same age. Their methods of working have been 

 observed by the writer under a binocular microscope, and corre- 

 spond very closely wuth those employed by Pityogenes hopkinsi 

 Swaine, which have been recorded in detail elsewhere (Blackman, 

 1915,^ pp. 16-32). When the brood-burrow is made in the trunk, 

 as it is in the great majority of cases, the entrance gallery, which is 

 cylindrical and of a diameter just large enough to accommodate 

 the insect making it, extends through the bark diagonally upward 

 at an angle of about 45 degrees. On reaching the surface of the 

 wood the male excavates an irregular shaped nuptical chamber 

 which lies partly in the bark and partly in the sapwood. 



The burrow is now ready for the females of which there are 

 usually several for each male. Each of these immediately after 

 her entrance begins to excavate a separate egg-gallery. In the 

 majority of instances these galleries run in a direction perpendicular 

 to the grain of the wood (Plate IV, fig. 2), although occasionally 

 some females follow a course parallel to the grain. There are 

 from one to five egg-galleries to each engraving. The following 

 tables present, in summary, various data derived from a careful 

 study of the engravings of Ips longidens. 



Number of Egg-galleries, Based on a Study of 118 Engravings. 

 Brood-burrows having one egg-gallery 10 



tw^o 

 three 

 four 

 five 



54 

 37 

 15 



2 



Average number of egg-galleries in a brood-burrow 2.53 



Length of Egg-galleries, Based on the Study of 50 Engravings. 



Average No. of gal- 

 length, leries studied. 



Uniramous burrow 25 . 37 8 



Biramous " 19.42 54 



Triramous " 17.5 24 



Quadriramous " 16.9 28 



Average length all types 18. 8 114 



> Cf. Blackman, 1915 Tech. Pub. No. 2, N. Y. State Coll. Forestry, pp. 15, 16. Blackman & 

 Stage, 1918 Tech. Pub. No. 10, N. Y. State Coll. Forestry, p. 46. 

 2 Loc. cit. 



