March, 1910.] OSBURN : STUDIES ON SyRPHID^. 65 



As to what has produced these abnormahties we can only con- 

 jecture. The presence of an extra antenna with the suppression of 

 the compound eye naturally recalls the experiments on Crustacea first 

 performed by Herbst* and since repeated by a number of investi- 

 gators, where by the excision of the compound eye at a certain level 

 an antenna was regenerated instead. This has been found to hold 

 true for a number of Crustacea, but the small amount of experimental 

 work bearing on this question in the insects does not seem to bear 

 out this explanation for the specimen at hand. Tornierf has pro- 

 duced forked antennae in various species of beetles on regeneration, 

 by cutting ofif the antennal joints at various levels, but his " Hyperan- 

 t^nnie " does not mean the presence of supernumerary antennae. 

 More recently Werber:}; extirpated the compound eye and antenna of 

 Tcnnchrio larvae and pupae, and found that in the only two cases 

 which reached maturity, the eye and antenna were regenerated almost 

 normally, so these experiments throw no light on the abnormalities 

 of this specimen. Even if we should accept the supposition that the 

 antenna represents the eye in this case, we should still have to explain 

 the presence of the extra vertical triangle. 



At first glance it might seem that the ocelli and triangle are here 

 replacing the compound eye, since they more nearly occupy the posi- 

 tion of that organ. It must be recalled, however, that the ocelli are 

 not in any way homologous with the compound eyes, since they are 

 innervated by different nerves arising from different lobes of the 

 brain, and according to the accepted theory of Grenacher§ are only 

 related in their probable development from primitive similar sources. 

 Unfortunately the specimen is dried and therefore not in a condition 

 to investigate as to the internal soft parts. It may be that the con- 

 dition is due to some injury of such a nature as to completely over- 

 throw the equilibrium of normal development during metamorphosis, 

 and if such is the case, further experimentation on the regeneration 



* Herbst, Ueber die Regeneration von antennenahnlichen Organen an 

 Stelle von Augen, Arch. Entw.-Mech., Bd. IX, 1899. 



t Tornier, Das Entstehen von Kafermissbildung, besonders Hyperantennie 

 imd Hymermelie, Arch. Entw.-Mech., Bd. IX, 1900. 



t Werber, Regeneration des exstirpierten Ftihlers und Auges beim Mehl- 

 kafer, Tenebrio molitor, Arch. Entw.-Mech., Bd. XIX, 1905. 



§ Grenacher, Untersuchungen iiber das Sehorgan der Arthropoden, etc., 

 Gottingen, 1879. 



