SCIENCE-GOSSIP. 



135 



the aperture is more sloping from top to base ; 

 there are also important differences in the arma- 

 ture, the lower horizontal parietal fold being very 

 short, not extending on either side beyond the two 

 lower arms of the main fold (see fig. 87c, which 

 shows part of the parietal wall with its folds). Of 

 the palatal armature, the first, second, and third 

 folds are more elevated ; the first is bilobed, and 

 above the posterior portion of the second occurs a 



very short additional fold. The vertical plate is 

 also more elevated, and in place of the usual 

 denticle posteriorly to its lower extremity is 

 found an elevated ridge quite united to the 

 plate. Fig. 87a shows the anterior and fig. 

 876 the posterior aspect of both armatures. The 

 specimen figured is in the collection of Mr. 

 Ponsonby. 



{To be continued.) 



ORIGIN OF SPECIES IN INSECTS. 

 By J. W. TuTT, F.E.S. 



(Concluded from page 112.) 



Climate Producing Useless Characters. 



"D OMANES considered that the actual causes 

 •^^ which lead to the production of useless 

 specific characters were climate, food, sexual selec- 

 tion and laws of growth. It may be well to examine 

 these points from our position as entomologists. 

 The influence of climate on Lepidoptera, and I have 

 no doubt on other classes of insects, is undoubted. 

 When the same species inhabits central Europe, 

 the Alps at high altitudes, and the Polar regions at 

 high latitudes, the forms from the various localities 

 often exhibit marked differences, and those from 

 high altitudes more or less tend to resemble those 

 from high latitudes. These differences may be 

 produced either by climate directly, or by a 

 difference in the nutritious value of the food 

 brought about by a difference of climate. According 

 to Staudinger, the variety aegidion of Plebeins argus is 

 confined to Lapland and the Swiss Alps. Polyom- 

 matus eros inhabits the Alps and Pyrenees ; a large 

 form known as var. eroides occurs in the plains of 

 south-east Germany. The var. polaris of Aglais 

 urticae is almost confined to the Polar regions. 

 Melitaea aurinia has a small undersized Alpine 

 variety known as inerope, whilst M. parthenie has a 

 similar form known as var. varia. Ossianns is a 

 small Lapland variety of Brenthis aphirape, and 

 Brenthis selene and B. euphrosyne have parallel 

 Lapland forms known as hela and Jitigal respectively ; 

 Coenonympha arcania has an Alpine form known as 

 darwiniana, and so on. We have the bright-red 

 form of Chrysophamis phlaeas from northern Europe, 

 the almost black form of the same species 

 appearing in the summer in those countries 

 washed by the Mediterranean. Yet, in neither 

 race, is the character a very fixed one, nor the 

 physiological change accompanying the change of 

 colour one that is hereditary, for the breeding of 

 the species from the dark form in more northern 

 latitudes results at once in the production of 

 specimens scarcely distinguishable from the normal 



form of the species occurring in our latitude. The 

 difference, then, may be due to the rapidity of 

 feeding up, so that the larvae do not get sufficient 

 material for use ; this, however, is unlikely. It 

 may be due to the rapid metabolism of the tissues 

 in the pupa, so that the normal pigment, if the 

 brighter coloured pigment be considered normal, 

 has not sufficient time to mature ; or it may be 

 that the pupa has not sufficient material at disposal 

 to form the pigment matter. I take it that the 

 second of these possibilities is the correct one. It 

 seems to me that this change of colour being due 

 to physiological causes, does not in any way affect 

 the specific characters of the species, and what is 

 true of this is true of all other Lepidoptera that 

 vary under different climatic conditions. 



When we turn to Mr. Merrifield's experiments, 

 where, as far as possible, all other factors have 

 been eliminated, we are much struck with the fact 

 that the exposure of the pupa to a difference of 

 temperature does, in some species, produce a 

 marked difference in the imago. This difference, 

 however, is not by any means identical even 

 with species of the same brood, yet we may 

 safely say that a general change in the same 

 direction takes place, under given conditions, 

 in the individuals of the same species, some 

 individuals showing much, others comparatively 

 little, change. The more extreme results, however, 

 of these experiments have not been the production 

 of useless specific characters, but have resulted in 

 the production of atavic forms, often quite unlike 

 any species now in existence. That these modifica- 

 tions take place only at the critical point of pig- 

 ment formation Mr. Merrifield has, I think, 

 abundantly proved ; and that the changes are due 

 to the effect of the high or low temperature on the 

 energy of the pupa at the time of the formation of 

 the pigment is, I think, certain. I am, therefore, 

 inclined to consider that climate does not — except 

 as (i) acting prejudicially or the reverse on insects 

 through their food, making it stunted and less 



