451] LARVAE OF THE TENTHREDINOIDEA—YVASA 133 



V. SUMMARY 



The larvae of the Tenthredinoidea have proved to be of great value in 

 affording important evidence in regard to the probable phylogenetic 

 relationship of the families included in this superfamily. The more 

 significant conclusions reached in this study are summarized in the form 

 of a synoptic key as follows: 



FAMILIES OF TENTHREDINOIDEA 



Larvapods present, thoracic legs present, well developed, distinctly segmented. 



Larvapods present on all abdominal segments Xyelidae 



Larvapods never present on 1st and 9th abdominal segments Tentkredinidae 



Larvapods wanting, thoracic legs present or wanting. 

 Thoracic legs present. 

 Thoracic legs and subanal appendages well-developed and distinctly segmented. 



Pamphiliidae. 

 Thoracic legs vestigial, indistinctly segmented. 



Subanal appendages and ocellarae present Cephidae. 



Subanal appendages and ocellarae wanting. 

 Metaspiracles vestigial, much smaller than abdominal spiracles. . . Xiphydriidae. 



Metaspiracles functional, as large as abdominal spiracles Siricidae. 



Thoracic legs wanting Oryssidae. 



A synopsis such as the foregoing is necessarily inadequate and some- 

 what misleading in indicating the affinities of the families. A better idea 

 is gained by means of the customary phylogenetic tree, altho such a 

 scheme also has its limitations. In the following diagram the relation 

 between the families of the Tenthredinoidea is shown. Here the relative 

 vertical positions are intended to represent approximately the degree 

 of specialization; and the continuous lines, the affinities. 



The larvae of the Tenthredinoidea are thus divisible into two distinct 

 groups. The first group includes the larvae characterized by the presence 

 of both the thoracic and abdominal legs, and by the absence of the subanal 

 appendages and suranal process, and is represented by the Xyelidae 

 and Tenthredinidae. The second group consists of the five families, 

 Pamphiliidae, Cephidae, Xiphydriidae, Siricidae, and Oryssidae, and is 

 divisible into two subgroups. The first subgroup contains the first four 

 families and is characterized by the absence of abdominal legs, by the 



