144 Lost or Mutilated Limbs of Insects — Oestlund. 



until after the next moult, when the same will expand and become 

 filled with the fluids of the body just as all the appendages 

 of insects are first formed within the skin of the pupa and on 

 emerging from the same expand. Such a reproduced limb is easily 

 distinguished by not acquiring the same size as the original, being 

 always somewhat smaller. 



The hexapods, or true insects, apparently make an exception, 

 as there is no case on record, as far as known to me, where a lost 

 or mutilated limb will be reproduced in comparison with the very 

 common occurence of this among the spiders and crustaceans. 



From the nature of the reproduction of a lost limb for the low- 

 er arthropods, which takes place only after a moult, it would follow 

 that the same would not be reproduced if lost after the last moult 

 has been passed. This is just the case with insects in the imago- 

 stage, and we have only to show that such a limb can be repro- 

 duced if lost or mutilated previous to the emerging of the insect 

 from the pupa, to put the hexapods on the same footing as the 

 lower arthropods in this respect. 



A fine specimen of Tremex^ one of the ''horntails" of the 

 hymenoptera, that I had the good fortune to find 

 some time ago, would seem to cast some light on 

 this subject. It is apparently a five-winged speci- 

 men, the left fore-wing of which, from some 

 cause or other, has become injured to such an 

 extent as to be of no further use for flight; less 

 than one-half of it is still left, torn up in threads 

 V ^- hanging down the body. Along side of this torn 



wing there is a second one that has grown out to take its place. This 

 additional wing has the characters of a reproduced organ, being 

 smaller and the venation less perfectly developed. What still re- 

 mains of the torn wing would indicate, on the other hand, that it 

 would have been of the same size as the right fore-wing, if not 

 injured. Both the hind wings show perfect development. Fig. 3. 

 Two explanations might be given for the condition of this 

 specimen. If we suppose, in the first case, that the injury to the 

 wing was received after the insect had emerged from the pupa, 

 the new wing would then have been produced irrespective of 

 moulting, a case v^^ich stands at variance with all known facts 

 in regard to the reproduction of lost limbs of arthropods. On the 

 other hand we may suppose that the injury was received while still 



