The Sirices appear to be most destructive insects to dead 

 trees and timber ; which is not surprising when it is stated, 

 that tlie eggs are deposited in clusters of two or three hun- 

 dred ; and the largest maggots, when full grown, are about 

 1^ inch in length. It is remarkable how much insects whose 

 . arvae are xylophagous vary in size ; for, whilst some speci- 

 mens o^ Sirex juvencus are as large as those represented in the 

 plate, others (especially females), from the same trees are not 

 more than a quarter the size. There are two species of this 

 fine genus found in Britain, the sexes of which are so dissi- 

 milar, that they have been described under four names. 



1. S. Gigas Linn. Jem. — Kirhy 8^ Spence, tab. ^. f, 1. — Don. 



6. 197. — S. Marisca Lhin. male: Panz. 52. 20. — psyl- 

 lius Fab. var.Jem. 

 June, rare. Pine and Lime-trees. Norwich, Wiltshire, 

 Kent, Berkshire, and in and near London. 



2. S. juvencus Lin7i. — Curtis Brit. Ent. pi. 253. 



July, August, and September. Fir groves, &c. ; Norfolk, 

 Suffolk, Hampshire, and Yorkshire. 



For a fine series of this insect, including the beautiful spe- 

 cimens figured, I am indebted to my kind friend the Hon. 

 Charles Harris, as well as for the following valuable observa- 

 tions relating to the destruction of fir-trees in the plantations 

 near Heron Court, the seat of the Earl of Malmesbury. 

 " With us," says Mr. Harris, " at the age of twenty the fir- 

 trees sometimes die to a great extent. The summer of 1825 

 or 1826 was peculiarly destructive to them, from its intense 

 heat and drought; and I am certain that I never saw any 

 trace of a Sirex except on dead trees. The smell of the tur- 

 pentine would fully account for this ; and if you remember, the 

 only spot where we could detect the Sirex in the standing 

 plantation of shorter trees, was on some dead stumps that had 

 evidently been overgrown by the others. The day after your 

 departure I went to visit the fir wood, when I had the good 

 fortune to extract eight males of the Sirex ; two of these I 

 purposely let go ; they proved very strong on the wing, and 

 ascended with a loudish hum to an invisible height." From 

 this it appears that the mischief arises from allowing dead 

 trees to remain standing or lying about ; and timber ought to 

 be well examined before it is employed in building ; for I un- 

 derstand that considerable numbers of the males have been 

 taken flying about the tower of York Minster, no doubt seek- 

 ing the females which were issuing from the timbers that sup- 

 ported the roof, and which would be, of course, greatly 

 weakened by the constant and continued operations of the 

 Larvae, as well as rendered more combustible by the multi- 

 tude of passages and the quantity of dust which they create. 



The plant is Lapsana communis (Common Nipplewort). 



