xxn SIRICIDAE 509 



capable of inflicting much injury to the person, it is probable that 

 the peculiar ovipositor is believed to be a sting. The eggs are 

 laid it is said to the number of 100 in the solid wood of fir- 

 trees, but not in perfectly healthy wood ; the reason for this, it 

 is thought, being that in a healthy tree the great affluence of sap 

 caused by the burrows and presence of the Insect would be in- 

 jurious to the latter. The Sir ex will, however, attack a perfectly 

 healthy tree immediately after it has been felled. The larva, small 

 at first, enlarges its burrows as itself grows larger, and thus the 

 wood of a tree may be rendered completely useless for trade pur- 

 poses, although there may be very little outward indication of 

 unsoundness. The larva (Fig. 342, C, larva of Tremex) is a pallid, 

 maggot-like creature, with six projections representing thoracic 

 legs ; there are no other legs behind these, but some slight pro- 

 tuberances take their place ; the terminal segment is enlarged, and 

 bears a hard spine. There is a difference of opinion as to the 

 duration of the life of the larva, Kollar saying that in seven 

 weeks after the deposition of the egg the maggot is full fed, 

 while others consider that it takes two years to attain this con- 

 dition ; the latter statement is more probably correct, it being 

 the rule that the life of wood-feeding larvae is more than usually 

 prolonged. After becoming full fed, the Insect may still pass a 

 prolonged period in the wood before emerging as a perfect Insect. 

 As a result of this it not infrequently happens that the Insect 

 emerges from wood that has been carried to a distance, arid used 

 for buildings or for furniture. A case is recorded in which large 

 numbers of a species of Sirex emerged in a house in this country 

 some years after it was built, to the great terror of the inhabi- 

 tants. The wood in this case was supposed to have been brought 

 from Canada. 



Fabre has studied l the habits of the larva of Sirex augur, 

 and finds that it forms tortuous galleries in the direction of the 

 longitudinal axis of the tree or limb, and undergoes its meta- 

 morphosis in the interior, leaving to the perfect Insect the task 

 of finding its way out ; this the creature does, not by retracing 

 its path along the gallery formed by the larva, but by driving a 

 fresh one at right angles to the previous course, thus selecting 

 the shortest way to freedom. By what perception or sense it 

 selects 'the road to the exterior is quite unknown. Fabre is not 



1 Souvenirs entomologiques : quatrieme eerie, 1891, p. 308. 



