347] LARVAE OF THE TENTHREDINOIDEA—YUASA 29 



and only indistinctly segmented in the Cephidae. When the appendages 

 are long and setiform, the relative length and color of the segments differ 

 in different species. In the Cephidae the appendages may or may not be 

 provided with accompanying setae near the proximal end, and these 

 setae may or may not form a continuous group with the setae on the 

 sternum. 



That these structures are true appendages of the segment is indicated 

 by the segmentation and by the fact that they are invariably articulated 

 at the proximal end against the surface, not being mere protuberances 

 like the caudal processes of the tergum. Some embryologists consider these 

 appendages to be homologous with the cerci of generalized insects and the 

 anal "prolegs" of lepidopterous larvae, and, therefore believe them to be 

 true appendages of the eleventh abdominal segment. It is obvious that 

 they can not be homologous with the anal larvapods of other tenthredinoid 

 larvae. Crampton (1919) designated them as arthrostyli on the ground 

 that they are apparently homologous with the styli of the Ephemeridae 

 and other insects. The opinions of entomologists differ, for example 

 Middleton (1921) homologizes the subanal appendages with the post- 

 pedes of Crampton. The homology and function of these appendages 

 need further investigation. However, it is significant that long distinctly 

 segmented appendages should occur in the Pamphiliidae and rudimentary 

 ones in the Cephidae. 



Larvapods. — The embryological data seem on the whole to support 

 the view expressed by Korschelt and Heider (1899), who say that "the 

 abdominal appendages of the caterpillars of the Lepidoptera and Hymen- 

 optera are to be regarded as true limbs," and that "limb-rudiments first 

 form on all or most of the abdominal segments, but they very soon dis- 

 appear on those segments which in the larvae have no limbs, while on the 

 other segments they are transformed into the functional prolegs." Graber 

 (1890) has shown that the so-called anal prolegs of Hylotoma are the 

 appendages belonging to the tenth or true penultimate abdominal segment. 

 They are, therefore, not homologous with the anal "prolegs" of lepidop- 

 terous larvae, which are, according to Graber (1890), the appendages of 

 the ultimate segment. 



The maximum number of larvapods {pig) occurs in the Xyelidae, where 

 each of the abdominal segments is provided with a pair. The first and 

 ninth pairs may be smaller than the others, as in Odontophyes, but they 

 are always discernible. The number of larvapods present in the Tenthredin- 

 idae varies from six to eight pairs. They are usually present on abdominal 

 segments 2-7 and 10 or 2-8 and 10, rarely on 2-6 and 10. In the Fenusinae 

 (Fig. 105) and Caulocampus the tenth pair is obsolete, and in Metallus 

 (Fig. 103) they are fused together forming a median protuberance. 

 Larvapods are entirely wanting in the other families of the Tenthredinoidea. 



