550 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



It appears that the Noctuidae (also the butterflies) are approaching com- 

 plete discovery in the Nearctic, but that the other groups are due for substantial 

 increase. The European list indicates that eventually there will probably be 

 more micros than macros. 



Morphology 



The development of knowledge of the external morphology of the Lepidop- 

 tera has been almost wholly of two kinds, either incidental to general studies 

 of the insects, like Crampton's work on a couple of types of Lepidoptera in 

 1908 and many later papers, or else by-products of classification studies. The 

 study of internal anatomy, however, has been independent. For the caterpillar 

 there has been nothing during the whole century in the class of Lyonet's 

 work in 1760, and for the adult, the dissection of the Monarch, published by 

 Scudder in the Butterflies of Eastern North America (pi. 62, 1888) stands alone. 

 Further work on the anatomy has been voluminous but widely scattered; the 

 fullest and most recent summary is that by Zerny and Beier in Kukenthal's 

 Handbuch (vol. 3, pt. 2, 1936). It shows a fairly complete knowledge of the 

 anatomy as a type, but there is still little on variation of structure within the 

 order. 



Physiology 



Physiologists as a rule make slight distinction as to the form they use, whether 

 Neurospora or Paramecium, Brosophila or man; only occasionally has a lepi- 

 dopteran been chosen as an object, and I think never for the sake of contrast 

 with other organisms. Quite recently Carroll Williams has been using cater- 

 pillars, chiefly the cecropia in the study of hormones and their relation to 

 transformation or the mechanism of respiration and hibernation, with their 

 controlling enzymes. Work on the nature of coloration has been more concen- 

 trated on the Lepidoptera, and it has been carried on for a longer period. Ma- 

 son pretty well settled the problem of structural colors in 1927, followed by 

 an actual electron photograph of the structures by Richards. But the question 

 of pigments has been much more complex, though in recent years a number of 

 workers, chiefly English, have done a good deal. 



The matter of pattern, as distinct from color, should probably be considered 

 morphology rather than physiology, since, though the elements generally appear 

 in pigment, the pattern has the same fixity as morphological characters; it evolves 

 from group to group in a similar way and is frequently foreshadowed by small 

 but definite differences of structure in the individual scales. The realization that 

 pattern elements have a fixity higher than the species or genus came pretty 

 early. In America we are apt to associate it with Smith's diagram for the Agro- 

 tids {Bull. U.S. Nat. Mus., vol. 38, 1890), but at the very beginning of our cen- 

 tury Guenee had a labeled type pattern {S2)ecies General, Noctuelites, pi. 1, 

 1851). The names of elements have been regularly applied to similar lines and 

 spots in other families, but it has only been gradually apparent that many of 

 these elements are homologous over a wide range of families. For the butterflies 

 in particular an independent nomenclature has been developd, most fully 

 worked out by Schwanwitsch (numerous papers, but the one on the Catagranuna 

 group [Trans. Zool. Soc, 1939, pt. 2] is best known). It is for the future to 



