138 BULLETIN 190, UNITED STATES NATIONAL MUSEUM 



joint pointed, yellow beneath, black above. Head blue-black, roughened 

 with coarse hairy scales on top ; inner eyelashes white ; occipital fringe 

 bright yellow. Thorax smooth, black ; collar of prothorax with broad 

 scales, blue-black; a yellow spot at base of forewing; tegula spotted with 

 yellow on posterior parts ; prothorax at the sides and beneath and fore- 

 wing at base beneath with yellow patches. Abdomen lustrous black, seg- 

 ment 2 broadly and segments 4, 6, and 7 narrowly, banded with yellow 

 above ; beneath, segments 2, 3, and 4 with yellow bands ; anal tuft short, 

 broadly rounded, black. Front legs black, coxae anteriorly at the sides 

 yellow, tarsi sand color; hindlegs black, tibiae rough above, chestnut-red 

 shading into orange ; first tarsal joint orange, terminal joints mostly black. 

 Forewing opaque, blue-black along costa, dull black inwardly, sparsely 

 mixed with reddish scales, heaviest along inner margin ; short, translu- 

 cent streaks before wing base ; discal mark not prominent ; outer margin 

 narrow, coppery brown, fringes dull brown ; underside dull brown, discal 

 mark reddish. Hindwing transparent, discal mark prominent, obliquely 

 elongate, brown black ; outer margin narrow, coppery brown, edged in- 

 wardly with dull brown scales ; fringes dull brown ; underside as above. 



Female. — Antennae simple. Abdomen banded with yellow only on 

 segments 2, 4, and 6; on the underside segments 3 and 6 narrowly edged 

 and segment 4 broadly banded with yellow ; anal tuft black, faintly 

 streaked with yellow above. Otherwise like the male. 



Expanse : Male 24 to 28 mm., female 26 to 32 mm. 



Distribution. — Eastern and Midwestern States ; Rocky Mountain 

 States ; Saskatchewan, Manitoba, Alberta, Canada ; Alaska. 



Type. — Male. In the Harrison collection, Boston Society of Natural 

 History (type and female paratype caught in copulation, Massachusetts, 

 June 20, 1829). 



Remarks. — The principal food plants of this species are willows, pre- 

 ferably shrubby, low-growing kinds. The larvae excavate long tunnels in 

 exposed roots, in canes and in branches, sometimes several occurring in 

 one cane or branch, but in separate burrows. Another favorite breeding 

 place is the galls and swellings produced by the larvae of cerambycid 

 beetles of the genus Saperda on willow, poplar, and aspen. On maturing 

 in the fall the larvae utilizes the upper part of its tunnel as a pupal 

 chamber, which is capped above and below and gives access to a circular 

 exit concealed under a flimsy cover of silk and bark. After wintering in 

 such chambers the larvae transforms to pupae late in May and during 

 June, and the adults emerge in June and July. The life cycle is two years. 

 Immature larA^ae winter in their tunnels, only mature lar\^ae in their 

 second year construct pupal chambers before hibernation. 



The European tabaniformis is identical practically with the North 

 American tricincta and would be considered conspecific but for some 

 slight structural differences in the male genitalia. Easily observable dif- 



