GENUS SIREX. 133 



The abdomen has no prolegs, but below the spiracles 

 the segments are developed into fleshy protuberances, 

 which project over the belly. There is no great differ- 

 ence, if any, in the size of the segments, until the four- 

 teenth is reached . This is much larger than the others ; 

 at the apex it is acute, and terminates in a sharp, horny 

 spine. At the base of this above is a projecting ridge 

 or tooth ; at the middle there is a similar tooth, there 

 being a gradual reduction in the thickness of the spine 

 with each tooth. In the centre of the segment above 

 is a deep depression, and on either side of this, at the 

 apex, is a short, blunt, horny tubercle. This part of 

 the segment is separated from the spine-bearing por- 

 tion by a depression. It bears some minute, brownish 

 setae, and there is a row of short tubercle-like setae in 

 front of the terminal spine. 



The larvae are found in various species of firs, feed- 

 ing internally in the wood, in which they bore galleries ; 

 and often, when they are numerous in a tree, they 

 completely riddle it. There seems to be a consensus 

 of opinion that the ? only lays her eggs in living 

 trees which are already diseased, ovipositing in those 

 places which show signs of decay. They will also lay 

 eggs in fallen trees. As an example of the way in 

 which they may infest a tree, it is stated by Mr. 

 Eaddon (Trans. Ent. Soc., i, p. 85, Append.) that 

 twenty feet of a fir tree from Worcester were so inter- 

 sected by the burrows made by the larvae that it was 

 only fit for firewood. From it the imagos came out 

 every morning, five or six coming out every day. The 

 females at first only averaged one in twelve ; after- 

 wards they became more numerous, and continued to 

 come out to the end of November, by which time only 

 females were produced. 



In this country the species seldom occur in sufficient 

 numbers to cause serious injury to the fir plantations, 

 but it is different in the large pine forests of Germany 

 and Northern Europe, where their ravages have been 

 serious. 



