ICHNEUMONID FINAL INSTAR LARVAE — SHORT 465 



Subfamily Mesoleiinae 



Figures 41-44 



Members of this subfamily are internal parasites of Tenthredi- 

 noidea.^" 



The dorsal part of the epistoma is unsclerotized or lightly sclero- 

 tized; the pleurostoma is usually lightly sclerotized: the hypostoma 

 and hypostomal spur are well sclerotized, the hypostomal spur being 

 relatively longer than in most Ophioninae; the stipital sclerite is well 

 developed and a lightly sclerotized cardo is sometimes present; the 

 labial sclerite is present and may be incomplete ventrally; in some 

 genera the dorsal ends of the labial sclerite bear small bubble-like 

 projections; a prelabial sclerite is present and two sensilla are usually 

 present on the dorsal part of this sclerite; the maxillary and labial 

 palps are relatively large and each bears two to three sensilla ; the silk 

 press is conspicuous; the labral sclerite is absent, except in Opheltes 

 and Protarchus; there are two main types of mandible, one having a 

 rounded and lightly sclerotized base with a relatively straight blade 

 which may be short, the other having a rather square base and a 

 curved blade; the antenna is disc-shaped; with the exception of Euceros 

 and Opheltes where the closing apparatus of the spiracle is small, the 

 spiracle has a thin-walled closing apparatus with a length which is 

 two to three times the depth of the atrium; the skin bears very small 

 setae and small projections which in Lophyroplectus are sufficiently 

 sclerotized to be described as spines. 



The Mesoleiinae have many features resembling the Ophioninae. 

 In the key to the subfamilies it was found necessary to separate the 

 Ophioninae into tribes in order to key out the Mesoleiinae from this 

 subfamily. The larval characters of the Mesoleiinae do, however, 

 indicate a fairly distinct group. The type of mandible of Rhorus, 

 with its rounded base and very small blade, is distinctive. The 

 mandible of Hypsantyx is basically similar although the blade is 

 relatively larger. The mandible of Hypsantyx, in turn, resembles that 

 of other Mesoleiini and that of the Euryproctini. The mandible of 

 Scolobates and Euceros is similar to that of most of the Ophioninae 

 in that there is a rather square base and a curved blade. But the shape 

 of the labial sclerite of Scolobates connects this genus to the remaining 

 Mesoleiinae. The labial sclerite of Euceros, with its plate-like expan- 

 sion of the ventral part, resembles that of some genera in the Ophio- 

 ninae, Campoplegini. In Opheltes (Mesoleiinae, Mesoleiini), however, 

 there is a smaller plate-like expansion of the ventral part of the labial 

 sclerite and this may connect to the condition in Euceros. The spu*acle 

 of Euceros, with its relatively small closing apparatus, resembles that 



2« Euceros frigidus Cresson has been recorded as an lntemalj)araslto o( Lepldoptera. 



