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



formity and simplicity in their instincts and habits than is 

 found in other groups ; they form no communities, nor, so 

 far as is certainly known, does " inquilinism " or " com- 

 mensalism " of any kind occur among them. We have, 

 perhaps, scarcely such evidence as would justify a positive 

 assertion that they are actually the oldest existing branch 

 of the Hymenopterous family-tree, but I can point to 

 nothing either in their structures or in their life-histories 

 which would render this view improbable. 



(a) The imaginal character which most definitely dis- 

 tinguishes the Sawflies from all other Hymenopterous Sub- 

 orders is the absence of any " constriction " at the point 

 where the so-called '"thorax" joins the abdominal seg- 

 ments which follow it. But this so-called thorax in the 

 Hymenoptera includes, besides the three truly thoracic 

 segments, a fourth (the " propodeum ") which has become 

 more or less incorporated with them during pupation, having 

 originally formed part of the abdomen. And it is really not 

 between the thorax and the abdomen, but between this 

 segment and the rest of the abdomen that the constriction 

 is situated. Accordingly, it might be correct to include 

 this segment always when counting the number of abdominal 

 segments, and in the case of the Sawflies it is not unusual 

 to do so. But in dealing with other Sub-orders most 

 authors commence their enumerations after the constric- 

 tion, so that what is really the 2nd abdominal tergite 

 is called the 1st, and so on. Since this remarkable con- 

 striction (which enables Wasps, Bees, Ichneumons, etc., 

 etc., to turn and twist in all directions the segments follow- 

 ing it, and thus bring their " stings " to bear on any part 

 they please of any creature attacked by them) is a character 

 peculiar to Hymenoptera and not developed in insects 

 generally, its entire absence in the Sawflies * is clearly a 



* Konow's name for the Sub-order, which is adopted in Rohwer's 

 Classification (1911), viz. Chalastoga'stra, meaning, I suppose, 

 (Hymenoptera) " with unconstricted abdomen," seems to describe the 

 real state of things more exactly than Lepeleticr's Sessiliventres and 

 other names that have been suggested (e. g. Symphyta as opposed to 

 Apocrita), which imply that the thorax and abdomen are fused to- 

 gether. This, so far as the basal segment of the abdomen (= pro- 

 podeum) is concerned, is the case with all Hymenoptera ! Another 

 name, employed in some other Papers of Etohwer, and of Enslin is 



Tenthrerfiimitlrti, but for philological and other reasons I have a 

 Special dislike to names formed after that pattern, and prefer to 

 accept ( 'halastogastra. 



