BEES, WASPS, ANTS, ETC. 



507 



in other cases slits are made into the leaves or other parts, and the eggs laid in these 

 slits. The slits are made by the peculiar ovipositor of the female. The principal part 

 of this organ is a pair of saw-like blades, which suggest the popu- 

 lar name of the family. 



/Selandria rosce, the rose slug, is an insect known in its larval 

 stage to all florists. The imported currant-worm, Nematus ven- 

 tricosuS) and the native currant-worm, Pristiphora grossularice, 

 are also well known members of this family. 



The family UROCEKID.E, or horntails, includes insects which are quite closely allied 

 to the saw-flies, but which differ from them in certain characters, especially in the 

 structure of the ovipositor or borer, and in the form and habits of the larva?. The 

 body of the adult is elongated and nearly cylindrical in form. This is well shown in 

 Sirex gigas. The male is furnished with a prominent horn at the caudal end of the 



FIG. 630. Selandria rosce. 



FIG. 631. Sirex gigas, male and female. 



abdomen, which suggested both the popular and the scientific names of the family. The 

 ovipositor of the female is attached near the middle of the ventral surface of the abdo- 

 men and extends far beyond the caudal end of the body. The principal part of the 



ovipositor consists of a boring apparatus by means 

 of which the female insect can drill a hole into solid 

 timber. These insects may often be found during 

 the summer months boring holes into living trees, 

 in which they lay their eggs. 



The larva? are wood-boring and often do great 

 injury to trees, the trunks of which they perforate. 

 They have six very small true legs, but no prolegs. 

 When fully grown they make cocoons of silk in 

 their burrows, interwoven with little chips which 

 they have made. After the pupal skin is cast off, 



the winged insect breaks through its cocoon, creeps 

 FIG. 632. Tremex columba. 



to the mouth of its burrow, gnaws through the 



covering of bark over it, and comes out of the tree into the open air. Tremex columba 

 has similar habits and often does considerable damage to shade trees. 



