xii INTRODUCTION. 



comparatively lethargic. Where the females are lethargic, the 

 larger body necessary to the development of a large number of eggs 

 is not accompanied by a correspondingly larger wing area, but in a 

 small measure, the conditions of the apterous females are followed and 

 the wings are frequently comparatively small. Many such examples 

 readily occur as in Lithosia pygmceola, Euchelia jacobcew, Nemeophila 

 russula, N. plantaginis, Ino statices, Nudaria senex, Setina irrorella, 

 Cosnobia rufa, Tapinostola fulva, Chortodes bondii, C. arcuosa, Stilbia 

 anomola, Acosmetia caliginosa, Hydritta palustris, Eusina tenebrosa, Epione 

 parallelaria, Halia brunneata, Scodiona belgiaria, Selidosema ericetaria, 

 Ematurga ato maria, Aspilates strigillaria, A. gilvaria, Mesotype virgata, 

 Ciedeobia angustalis, Scopula alpina, Chilo phrogmitellus. Crambus sail- 

 nellus, Eridopsela fractifasciana, Catoptria ccecana, Aplielia osseana, 

 Pleurota bicostella and very many other species besides. In those 

 mentioned, however, there can be no doubt that the less activity of 

 the females is accompanied by a more or less atrophied condition in 

 the development of the wings, or the wings are not developed pro- 

 portionately to the extra development of the body. But this condition 

 of things is the exception, and only shows us the connection between 

 habit and actual effect. In lepidoptera, generally, the females are not 

 particularly lethargic but almost as active as the males, and hence the 

 females with their proportionately heavier bodies have a greater wing 

 area, and are altogether larger than the male. To write the names of 

 those lepidoptera in which this is so, would mean writing a large part 

 of the British fauna. I will therefore only give a few examples. 

 Among the butterflies, Apatura iris is perhaps the most striking illus- 

 tration, whilst among the moths Endromis versicolor, Saturnia carpini, 

 Lasiocampa quercifolia, Bombyx quercus, rubi, castrensis, nemtria, Erio- 

 gaster lanestris, Odonestis potatoria, Cossus ligniperda, Zeuzera pyrina, 

 Hepialus sylvinus, velleda, Arctia caia, Ocneria dispar, Heterogenea 

 limacodes, Stauropus fagi, Nonagria typhce, N. lutosa, Neuronia popu- 

 laris, Angerona prunaria, Metrocampa margaritaria, Cataclysta lemnata, 

 Paraponyx stratiotata, Galleria mellonella, Melissoblaptes bipunctanus, 

 Aphomia sociella, Ptycholoma lecheana, Sciaphila nubilana, Orrhotcelia 

 sparganella, Leioptilus micro dactyla etc., are striking examples from the 

 different families, which illustrate this general rule. The females of 

 Arctia caia, Spilosoma lubricipeda, S. menthastri and many other species 

 just mentioned, pair where they emerge, or after a very trifling flight. 

 They then lay a batch of eggs where they pair, and so are much 

 lightened for the future flights they take, and this appears to occur 

 very frequently in large and heavy-bodied moths even with a good 

 wing expanse. Geddes and Thomson write: "Among insects, the 

 more active males are generally smaller, and often very markedly," 

 although it is doubtful whether they understood to what actual extent 

 this was so. It will be thus seen that " size " is frequently a marked 

 secondary sexual character, although the greater or less size may be- 

 long to either sex in different families. Geddes and Thomson consider 

 this difference of size due to a more sluggish conservative habit of body 

 in the female, but does this really reach the root and basis of the sub- 

 ject. Is not this a self-evident statement rather than a real probing 

 as to the actual cause ? In our insects, is not the larger size of the body 

 of the female due essentially to the large size and weight of the ovisacs 



