HYMENOPTERA 



507 



Ori/ssus abietinus very closely resembles C. sayi (Fig. 341); 

 it has indeed been recently suggested by Mr. Harrington that 

 the two supposed species may really be identical. 



Fam. III. Siricidae or Uroceridae. 



Pronotum closely connected ivith the mesonotum, perpendicular in 

 front; the anterior lobe of the latter not separated by the 

 lateral lobes from the posterior lobe : the median plate (behind 

 the metathorax) is divided longitudinally along the middle. 

 The female is provided at the extremity of the body tvith an 

 elongate,- cylindrical boring instruvient. The larvae live in 

 the ivood of trees. 



Fig. 3i2. — Tremex 

 columba. Nortli 

 Americu. A, 

 Imago, female : 



B, pupa, female, 

 ventral aspect : 



C, larva ; a, im- 

 perfect legs : D, 

 parasitic larva of 

 Thalessa. (B 

 ami D after 

 Eiley.) 



The Insects of this family are usually of large size and of 

 bright conspicuous colours ; these, however, frequently differ 

 greatly in the sexes of the same species, and may be very vari- 

 able even in one sex. The antennae are filiform and usually 

 elongate ; the head is usually contiguous with the thorax, but in 

 one division, Xyphidriides, it is exserted and separated from the 

 thorax by a well-marked neck. The pronotum is attached to 

 the mesonotum, and possesses very little, if any, freedom of 

 movement ; it varies in its size, being sometimes conspicuous 



