86 OUR HOUSEHOLD INSECTS 



much more thickly than at the ends, and show a 

 tendency to form two distinct rows. It is obvious that 

 this arrangement greatly increases the power of the 

 wings, and no doubt largely contributes towards that 

 vigour of flight which is so prominent a feature in 

 the Hymen optera. 



The larvae are fat whitish maggots, with six very tiny 

 feet in front, and the tail ending in a spine ; and from 

 their size, it will be easily understood that they work 

 great havoc in fir trees in which they have established 

 themselves, devouring, as they do, the solid timber. 

 When the insect reaches the end of its larval life, it 

 forms a silken cocoon in its burrow, and in this changes 

 to a pupa, which, as is customarily the case amongst the 

 Hymenoptera, looks like a mummy of the perfect insect. 

 In this same burrow it enters on its perfect life by cast- 

 ing its pupal skin ; but when thus freed, it has still to 

 make its way into the open air ; its burrow has already 

 been carried as far as the bark of the tree, and it there- 

 fore has now to perforate the bark in order to escape 

 from its prison. This it does by gnawing through it, 

 and then creeping through the opening thus made. It 

 often recruits its strength after its exertions by sitting 

 on the tree trunk just outside for a time, before starting 

 on its noisy flight. 



When domiciled with man, however, its escape from 

 its prison-house is not always so easy. At a military 

 clothing-store in France, one of the shelves on which 

 the clothes were piled contained a pair of Sirices, pre- 

 sumably in the larval condition when first introduced. 

 On arriving at maturity, the insects proceeded to work 

 their way out of the wood as usual, but when they 

 reached the surface they found their further pro- 

 gress barred by the piles of clothing, which happened to 



