46 
that temperature has played in the production of such seasonal 
dimorphism. Even when the characters of insects, as exhibited by 
their markings and coloration, are so firmly fixed that the direct 
influence of temperature has little effect on them, the action on more 
amenable (less fixed) allied species may give us valuable clnes as to 
the evolution of the colours of the more fixed species. 
These experiments suggest, too, that they may aid in the elucida¬ 
tion of facts connected with other lines of inquiry. One of these at 
once suggested itself to me on looking over Mr. Merrifield’s material. 
This was that a clue might often be obtained as to the geographical 
origin of many species. It is found that under these experiments a 
high temperature has an advantageous effect on some species, a dele¬ 
terious effect on others. Conversely a low temperature produces fine, 
well-developed specimens of some species, whilst it stints and destroys 
the pigment of others. Here is a suggestion that the insects which 
are advantageously affected by a high temperature reach their point 
of greatest vitality in, and probably spread to us from, lower lati¬ 
tudes ; whilst those which are advantageously affected by a low tem¬ 
perature probably reached us from higher latitudes. If this idea can 
be worked out, it will be seen that Mr. Merrifield’s experiments may 
have a direct influence in answering some of our questions as to 
geographical distribution. 
A practical application of this occurs to me. Mr. Percy Bright 
(Ent. Rec., viii., p. 307) referring to the abundance of the dark aber¬ 
rations of Limenitis sibylla in the New Forest, during the last summer, 
says : “ The characteristics of the weather from March to the middle 
of August, were a great excess of sunshine and a lack of moisture. I 
do not know whether these were the causes. It would be very 
interesting to know if, in dry, hot climates, this particular insect 
showed this tendency to melanism.” It would appear, from what I 
can learn of the geographical distribution of this species, that it is 
nowhere an inhabitant of hot climates. It appears to be confined to 
Central Europe, and not to extend even into Southern Europe. 
The dark aberrations appear to occur sporadically, and to be nowhore 
common. One cannot therefore say that it does show a tendency to 
melanism in hot climates. It happened, fortunately, that this was 
one of the species upon which Mr. Merrifield had recently experi¬ 
mented, and it was evident, from an examination of the specimens 
which be had bred, after subjecting the pupae to a high temperature, 
that the latter had acted most prejudicially upon them. The ground¬ 
colour was pallid, the colour ill-developed, but there was no trace of the 
narrowing of the white bands, nor a tendency to melanism in any of 
the specimens. Another explanation, besides the high summer 
temperature of 1896, will probably have to be found to explain the 
peculiar melanic development which took place in the New Forest 
specimens of this species this year. 
Another suggestive point presents itself. I observed, in looking 
over Mr. Merrifield’s specimens, that various species of Saturnia and 
Bombyx showed a common tendency, when the pupae had been exposed 
to a high temperature, to assume, in the resulting imagines, a ruddy 
hue. The alliance between the Saturniids and true Bombycids is still 
a moot point, but this change to a common tone under the same cir- 
