112 [M^y. 



jrroiap in this country, these small bees exhibiting considerable sexual and 

 other variation, so that they are a difficult stud}'. I should be very pleased to 

 examine series of the various forms from different parts of the country, provided 

 they have locality labels with the date of ca^jture. — E. C. L. Perkins, Park 

 Hill House, Paignton, April Uth, 1918. 



llie Wiiujless Geometer. — In liis criticism of my note in last month's 

 Magazine, Mr. Porritt has, I think, misxmderstood the gist of my remarks. 

 The suggestion I threw out was, that as disuse leads to the loss or deterioration of 

 an organ, so disuse must have been the cause that led to the wingless conditiciu of 

 certain insects, and that the cause of the disuse simply lay in a natural indisposi- 

 tion on the part of the insect to use its wings. That the notion is not a fanciful 

 one, and that a sluggish disposition does exist, we have evidence every day in the 

 lesser activity of one insect as compared with another, and by tlie greater 

 sluggishness in a general way of the female over the mal(>. But there are 

 many degrees of it, and whenever it threatens to become excessive to the 

 detriment of the species, natural selection steps in and wipes it out. On the 

 other hand when no disability ensues, but rather the reverse, the sluggish habit 

 gets more and more confirmed as one generation follows another, until by 

 constant repetition it becomes absolute and the desire to fly is completely lost. 

 Then, and only after a further lapse of time would degeneration begin to set 

 in. How long that might be it is impossible to say, but surely much longer 

 than the comparatively few years dviring which entomology has been studied, 

 and which Mr. Porritt believes sixfficient to bring about appreciable changes.* 



The case of Coleophora inulse was merely given as an instance in a vei-y 

 striking degree of this sluggish disposition, but it was not meant to illustrate 

 the highest or absohite stage of it. Quite recently, and sonaewhere in the 

 interval between the draining of the original pond and its subsequent refilling, 

 the insect must have used its wings to reach the spot. Even had the locality 

 not been destroyed, I believe it would at some future time have left of its own 

 accord. Exceptional circumstances might be expected to arise, leading to an im- 

 usually large and vigorous brood, when under the excitement so connuonly 

 associated with crowds, either of men or animals, the whole colony would have 

 taken wing and migi-ated. 



Mr. Porritt's experience with the Hy))ornias was a most interesting one. I 

 suppose that the weather was very favourable at the time and that there 

 had been a great and simultaneous hatching out just when Mr. Porritt came 

 across them. But it would have been still more interesting could he have told us 

 the condition of things a day or two later, and whether the females were still 

 on the tree trunks and the males at rest under the leaves. I should scarcely 

 expect they were ; biit rather that, pairing having taken place, the females 

 had moved up into the branches for better security, and the males, their 

 function over, had for the most part perished. Besides, however suitable dead 



* When during the past thirty to fifty j'cara, we have seen altered external conditions for 

 enviro:iment entirely change the colour — we might almo.st say from white to black— in so many 

 species of Ltpidopti i-a ; it does not seem unreasonable that in a hundred years we should expect 

 to be able to detect at least some fractional difference in the size of abbreviated wings, if a process 

 of reduction were going on.— G. T. P. 



