of the Group Callidryades. 411 



omitted to include the CalUdryades. Perhaps, as the group 

 contained no undescribed species, I hardly felt justified in 

 occupying official time upon it whilst other groups urgently 

 needed attention. Now that I have time to spare, I think it 

 advisable to point out that many of the supposed species 

 recorded in my ' Monograph of CaJUdryas* published in 1873, 

 as well as one or two described subsequently, are unquestionably 

 only seasonal phases of other species. 



I have been asked recently, as in the past I asked others, — 

 " How do you know that these forms which you put together 

 are only phases of one species?" 



When we take up the study of any branch of natural 

 science we find that Nature works by rule. It is now known 

 definitely that among the Satyrinse the wet phases are 

 ornamented with well-defined ocellated spots, which in the 

 dry phases are either greatly reduced in size (the pupils alone 

 being left in some cases) or are wanting altogether. 



In some butterflies the wet phases have the apex of the 

 primaries produced into a long process, which is greatly 

 reduced or wanting in the dry phases. In many the under 

 surface of the wings in the wet phase has a defined pattern 

 in brilliant colours, whereas in the dry phase this surface is 

 blurred and so coloured as to resemble a decaying or withered 

 leaf. 



In the Pierina? all silver spots tend to disappear from the 

 under surface in the dry phase ; as a rule, heavy borders or 

 conspicuous markings disappear or become less prominent ; 

 in many species pink or sandy colouring is seen on the 

 secondaries and the apical area of the primaries below. In a 

 word, the butterfl}'- is so coloured as to be least conspicuous 

 amongst its dry surroundings. 



Enough species have been bred by experienced field- 

 entomologists to prove that tiiese marked diflferences are 

 authentic ; therefore, whan we compare two forms from the 

 same locality \Yhich only differ precisely as the seasonal 

 phases of one species ought to differ, and particularly when 

 we find individuals of one of these forms which in some of 

 their characters show gradation towards the others, we are 

 fully justified in concluding that they are conspecific. 



"When a wet or a dry phase is not required for the 

 preservation of a species, it tends to disappear, so that the 

 insect eventually becomes monomorphic; but in some cases all 

 the gradations between tiie extreme phases persist and the 

 species becomes polymorphic, as in Precis archesia, which 

 exhibits seven fairly defined gradations. 



The typical CalUdryades are now divided into six genera, 



