312 Rev. F. D. Morice's Notes on Australian Sawflies. 



number of questions which I have found very interesting 

 even when I have failed in answering them to my own satis- 

 faction. Let us inquire, then, how the typical members 

 of these sections differ — first, as to their Bionomics ( = the 

 life-history of the individuals in each group), and afterwards 

 in other ways, some of the latter differences being apparently 

 consequent on the former. 



{a) The food of their larvae differs, though in both cases 

 alike it consists exclusively of vegetable tissues. The 

 typical Siricidae feed on timber of some sort, perhaps never 

 quite sound and sometimes actually rotten; the Tenthre- 

 dinidae on fresh leaves, which in some cases are devoured 

 entirely, in others merely skeletonised, or more or less 

 emptied of their " parenchyma." 



(b) The special mark of the Tenth' edinidae, however, is 

 not so much the precise nature of their food — for leaves are 

 also eaten by certain genera (Pamphilius, etc.) which in 

 other respects differ considerably from any typical Tenthre- 

 dinid — as the circumstances that (i) they are able to move 

 freely about the substances on which they are feeding, and 

 that (ii) while thus moving about they are usually fully 

 exposed to view, or at most imperfectly screened by the semi- 

 transparent cuticle of a leaf within whose interior they are 

 feeding. Larvae of Siricidae. on the contrary, issuing 

 from eggs deposited at the bottom of a deep and extremely 

 narrow hole in the interior of timber, find themselves 

 hemmed in on all sides by material through which they can 

 only pass by gnawing a tunnel out of it with their jaws, 

 and afterwards forcing themselves forwards into this tunnel, 

 so as to continue the operation, with the help (as it is 

 believed) of assort of horny spike, which arms the other 

 (anal) extremity of their body. Continuing this progress, 

 which must, of course, be slow and practically always in 

 one direction, they gradually pass by a tunnel which grows 

 wider and wider as they themselves increase in size from 

 the interior of the timber towards the world outside ; but 

 do not actually emerge into it till they have completed their 

 metamorphoses and are no longer larvae bui imagines. 

 Accordingly, (i) their movements are not free, but severely 

 limited, and (ii) they are under cover, and indeed buried 

 in absolute darkness, during the whole of their larval 

 life. 



('■) Evidently connected with these differences in the 

 bionomics of the two groups are certain other differences 



