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pre^actou6 & iparaeitic lenemiea of apbibea 



(JncluMnc} a StuD^ ot Ib^per^parasltes). 



By H. C. a. Vine. Plates III. & IV. 

 J^ar^ II. — continued. 



IN studying the anatomy of the Aphidivorous Syrphidse, 

 perhaps no point will more strongly fix the attention, even 

 of a very casual observer, than the vast difference in the 

 structure of the alimentary systems of the larva and the imago. 



The exclusively animal food of the larva is obtained and 

 assimilated by organs whose special adaptation for the purpose is 

 remarkable, even in a section of the animal kingdom teeming 

 with remarkable and extraordinary structures. In the imago the 

 wholly vegetable diet is taken into the system by the most com- 

 plex and delicate suctorial organ known, and applied to the 

 maintenance, and more especially to the reproduction, of life by 

 equally elaborate alimentary and excretory organs, which present 

 many points of resemblance to those of graminivorous animals. 



I am quite aware that similar changes of food and structure 

 prevail throughout the diptera, and in a less degree among many 

 other insects ; but I do not know of any group (unless among the 

 Neuroptera) in which the contrast is so complete, for the larvae of 

 Aphidivorous Syrphidae are not only carnivorous, but they hunt 

 and kill the creatures they require for food. 



The Mouth Parts of the Larva. 



In the Aphidivorous Syrphidae the mandibles are represented 

 by a pair of strong hooks attached to a chitinous foundation, 

 situated on either side of the ventral folds of the epidermis, behind 

 the opening of the mouth, and immediately behind and beneath 

 the frontal papillae. When the larva is in a state of repose, they 

 are hidden within the body, and appear when the evagination of 

 the mouth parts has proceeded sufficiently for the papillae to 

 become visible (PI. III., Fig. 5,^,^). 



These hooks (PI. III., Fig. 7) are broad at base, short, hooked 

 slightly, and sharply pointed. They are unarticulated in any way, 

 and appear to derive their power of movement from the flexibility 

 of the derma, of which they are a process. A muscular band 



International Journal of Microscopy and Natural Science. 



Third Series. Vol. V. d 



