As soon as the maggot leaves the inner chamber the irritation ceases 

 and the wound begins to heal. The cambium grows down into it year 

 after year, and the annual growth of wood formed there slowly covers 

 it over until in three or four years it is completely buried (fig. 5) 

 beneath the new growth and thus forms the black check. 



As the wood grows down into the wound in healing it over, a depres- 

 sion is formed in each new layer, but sometimes the new layer thickens 

 around the depression and forms an elevation above the surrounding 

 surface. In both cases an ornamental curl is formed that will show as 

 a bird's-eye effect in bastard-sawn or longitudinal sections of the wood. 



Pig. 5.-0, Longitudinal section of wood containing a black check; b. the check; c, the stain in 

 the wood beneath it ; d. the curls in the wood covering it ; e, the resin m ass on and in the bark ; 

 f. section a split into four sections to show tangential views; a, tangential view of check. 

 h h. tangential view of curls; i, black spot or old resin mass (original). 



NATURAL ENEMIES. 



Two hymenopterous parasites were bred from the syrphid puparia. 

 Dr. Wm. H. Ashmead, of ,the U. S. National Museum, identified one 

 of these as an ichneumonid (Stjrphoctonus maculifrons Cr.) and the 

 other as a chalcidid (Eutelus flavipes Walk.). Both species are fairly 

 common, and probably aid greatly in keeping the trouble in check. 



Syrphoctonus maculifrons Cr.— This is a small wasp-like ichneumon 

 fly about 0.36 inch in length. It has a dark body marked by a 

 few white patches at the bases of the wings and legs. The face is 

 nearly covered by a square of white, and the legs are reddish brown. 

 The abdomen of the male is more slender than that of the female, and 

 the white square on the face is larger. The earlier stages are not known. 

 Pupation takes place in the body of the maggot in the outer resin mass. 

 The adult emerges during the latter part of June or the first of July. 



