BEUTENMULLER, MONOGRAPH OF THE SESIID^E. 



227 



polistiformis, M. dollii, and Podosesia syringes mimic certain species of paper-wasps 

 belonging to the genus Polistes. The female of Sanninoidea exitiosa so much 

 resembles the red-banded species of Pompilus that it is a very difficult matter to 

 distinguish them when flying in the field. 



Characters of the Larv,e. ! 



So far as known, the larvae of the Sesiidae are all internal feeders, restricted 

 to the habit of boring in more or less woody stems. There is, therefore, little 

 need for diversity of structure or special adaptations. Indeed, the similarity of 

 habit would tend to convergence in the general structural features. Further 

 there is no need for the development of coloration, as the larvae feed entirely 



Tlrothorcty fa iiotho ra.-y. 





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Fig. 4. 



Fig- 5- 



Fig. 



concealed. We find all the species white without markings. The result is that 

 the several larvae are very similar. 



The Sesiid larva partakes of the usual structure of the lepidopterous larva, 

 exhibiting a low type, allied to the Cossidae (also wood-borers) and to certain 

 families of the Microlepidoptera. It comes nearest, perhaps, to some Tortricid 

 forms. The head (Fig. 4) is rounded, with the apex retracted below the pro- 

 thorax, a very high clypeus, small antennae and weak ocelli, the lower posterior 

 one often obsolete. The body is normal or somewhat flattened, feet normal, the 

 abdominal ones short or nearly sessile, with well-developed crochets in a single 

 transverse ellipse, narrowly broken on both outer and inner sides, not composed 

 of alternating long and short hooks, but all uniform, the outermost gradually 

 smaller. Contrary to the condition in some other boring larvae, the shields are 

 not strongly developed, but degenerate. Cervical shield and anal plate large, 

 but weak. Tubercles moderate to obsolete, usually small and degenerate ; setae 

 moderate. The abdominal setae are arranged as in the Cossidae, Pyralidae, and 

 Tortricidae, tubercles iv and v united, one above the other. The thoracic tubercles 

 (Fig. 5) show certain peculiarities : on each half of the cervical shield are six 



1 Prepared by Dr. Harrison G. Dyar. 



