39 



On Insect Teratology (Remarks to Introduce a Dis- 

 cussion on " Teratological Specimens"). 



By T. A. Chapman, U.D., F.Z.S., F.E.S. J^ead October 27///, 



1 910. 



It so happens that since this discussion was proposed I have 

 met with two specimens well worth describing, so that I am able to 

 add them as items to this paper, giving it a value I had no hope of 

 when I first found myself committed to it. These are Mr. Burrows' 

 very remarkable example of Acronycta tridens (PI. II), and one of 

 Lafiorina orbititlns, affording a little more of the history of diminutive 

 wings than we usually obtain with such specimens (Pi. I). 



The subject of " teratological specimens " is a vast one, but I 

 assume, rightly or wrongly, that the specimens are chiefly to be those 

 of Insecta, and more particularly Lepidoplera. 



What is a "teratological specimen"? There seems to be a 

 necessity for this periphrasis, as the simple term " monster," literally 

 " something remarkable," has gradually come to mean something 

 remarkable merely for size, probably because, I suppose, size is the 

 quality that most easily strikes our attention. 



"Monstrosity" is now in use in the sense of a teratological specimen, 

 but strictly speaking monstrosity is a quality, not a thing. " Mal- 

 formation" is perhaps as useful a word as we have, now that "monster" 

 has an ambiguous meaning. 



When we come to the actual definition of a teratological specimen 

 or malformation, we find the difficulty of doing so arises from the 

 want of a very definite line, separating it on the one side from a 

 variety or aberration and on the other from a result of injury. 



A malformation is the result of development taking place in an 

 irregular way, and therefore, as a rule, for purposes of definition we 

 may say it always arises from some interference with the germ-plasm, 

 preventing its normal progress. A monstrosity differs from a variety 

 in this, that a variety might be the normal forni of a possible, closely 

 allied, species ; a monstrosity seems very unlikely to be normal for 

 any species. 



As regards injury, it is probable that all malformations are, in fact, 

 caused by some injury, /. e. they all originate in the germ-plasm, 

 which develops abnormally, owing to some external interference. 

 By this, I mean more than an abstract proposition that germ-plasm 

 in normal circumstances will develop normally, but that there is 

 evidence that actual injury produces monsters, as, for instance, 

 M. Dareste's experiments on the eggs of the domestic fowl. 



