5 I O HYMENOPTERA CHAP. 



able to suggest any sort of perception that might enable the larva 

 to pursue the right course, and considers it must be accomplished 

 by means of some sensibility we do not possess. Fabre's observa- 

 tion is the opposite of what has been recorded in the case of S. 

 gigas, where the larva is said to prepare the way for the exit of 

 the perfect Insect. 



Individuals of Sirex are often found in dried and solid wood, 

 encased by metal When the Insect finds itself so confined, it 

 gnaws its way through the metal, if this be lead, and escapes. 

 The perseverance displayed by the Insect in these circumstances 

 seems to indicate a knowledge of the direction in which liberty 

 is to be found. 



About 100 species of Siricidae are known. They form two 

 sub- families : 



1. Siricides : back of head nearly or quite contiguous with the pronotum. 



2. Xyphidriides : back of head separated from the pronotum by an elongate 



neck. 



We are reputed to possess in Britain two species of each of 

 these sub-families, but it is doubtful whether more than one 

 Siricid is truly native. Sirex gigas is frequently brought over 

 in timber, and certainly breeds at times freely in Britain. Mr. 

 Leech has recorded the occurrence of the larvae in abundance 

 in fir-trees in the neighbourhood of Dublin. Sirex juvencus 

 is more rarely met with. Xyphidria camelus is doubtless a 

 native, though now apparently rare. It used to occur about old 

 willows, near London, in the New Forest, and, I believe, also 

 in the neighbourhood of Cambridge. 



Fam. IV. Tenthredinidae Sawflies. 



Hymenoptera Sessiliventres, having the pronotum small, accurately 

 adapted to the mesonotum ; the anterior lobe of the latter is 

 widely separated from the posterior ; there are two spurs on 

 the anterior tibiae. The larvae usually live on leaves after 

 the manner of caterpillars, but a few inhabit galls. 



The sawflies are an important family of Insects, their species 

 being numerous, while some of them are, in the larval state, very 

 destructive to vegetables and fruit. Being quiet creatures, rarely 

 seen on the wing, they are, though common Insects in thir; 



