158 



MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



reel or marked with yellow. It is found in pines, firs, and spruce 

 throughout the West. S. aerolatus Cress, is another metallic-blue 

 species (fig. 78), with black legs and smoky wings. This species 

 commonl}^ attacks redwood, cypress, and cedars, but it is also found 

 in pines, firs, and other conifers. S. helirensii Cress, is a smaller 

 species, five eighths of an inch in length, with head and thorax blue 

 black and the apical segment of the abdomen reddish brown. The 

 larvae infest ponderosa pine and sugar pine and have been found 

 also in Monterey cypress. 



Figure 79. — Hemlock bark maggot {Cheilosia alafikensis) : m, Resin mass with exit liole. 

 adult fly having emerged ; n, longitudinal section of similar mass, showing wound in 

 inner bark and outer sapwood, pupal chamber and exit hole in outer pitch mass, and 

 original beetle entrance connecting them ; o, healing wound in inner bark beneath mass 

 like that shown at m ; q, longitudinal section of wound p ; r, maggot ; s, puparium ; t, 

 pupa ; u, adult male ; v, head of female ; w, head of larva ; x, antenna, r, s, t, u, and 

 I' X 2 ; w X 20; a? X 45. (Burke.) 



Xem caudatus Cress, is a very long, slim species, with an ovi- 

 positor as long as, or longer than, the body. The abdomen is wholly 

 black and the legs yellow. The favorite host apears to be lodgepole 

 pine. X. morrisoni Cress, is similar but has a reddish abdomen. 

 It attacks firs and lodgepole pine and probably other conifers. 



BARK MAGGOTS 



Pecular defects in the lumber of certain coniferous trees, con- 

 sisting of dark-brown or blackish resinous scars, with the wood 

 thickened and curled, are made by bark maggots of the genus 



