THE vSYRPHIDAE OF OHIO 27 



directed into ever}^ corner of the body and even into the bases of the 

 appendages as they pick and suck out the soft contents. The skins, abso- 

 lutely empty, are then discarded by retraction of the segments, the 

 hairs or spines on those outside ser\'ing readily to dislodge the skin. 

 These dead skins usually drop down or blow away but may sometimes 

 be seen in numbers on the host-plant. 



As described above, the larvae of Eristalis spp. have rather special- 

 ized, soft flaps around the mouth which have a habit of opening out and 

 folding in, so as to create a current of water toward the mouth. Parti- 

 cles suitable as food are doubtless selected from the current by the action 

 of the "lips." 



As described by Ashmead the larvae of Mesogranniia poUta elongate 

 the anterior segments, protrude and puncture the saccharine cells of the 

 corn and suck up the exuding juice. 



The mouth of the larva of Microdon is located in the midventral 

 line near the anterior end of the body. There is little more than a longi- 

 tudinal slit, within which the mouth parts are located. A very slight 

 fold in front of this, however, bears the structures which I believe may 

 represent antennae. Wheeler states that in life the anterior end of the 

 body is occasionally raised for a few moments and one may see the small 

 pointed "head" of the larva moving about uneasily under the fringed 

 border as if in search of food. The mouth-parts consist of chitinized 

 structures which are evidentl}^ suitable for prehension and mastication of 

 food particles. 



The stout, formidable-looking spines of some larvae, as in Dideafas- 

 cita and Paragiis bicolor, iwax be protective. Some larvae take up pro- 

 tected positions on the under side of the leaves and twigs of the host-plants 

 or, in the case of cabbage, they are sometimes found among the inner 

 leaves, or at the axils of the outer leaves. It seems certain that the tough 

 skin and spine-like ornamentation of the larvae of Microdot are pro- 

 tective. Wheeler relates that in an artificial formicary the ants "killed a 

 young larva that had failed to get hold of a surface with its vulnerable 

 creeping sole. They turned the helpless creature over on its back and 

 for two days kept licking and biting it till it was reduced to a mere granule." 



The larvae of certain aphidophagous species present what seem to me 

 to be good cases of protective coloration. In a general way it may be said 

 that these larvae are never conspicuous. ( reneralh^ they are more or less 

 completely surrounded, or covered, with the aphids on which the\- are 

 preying, and therefore easy to overlook. P.ut in some cases there is added 

 to this a very close similarity in coloration between the larvae and the 



