[_Communicated by_ Mr. W. H. EDWARDS, _November 18th, 1879_.]
EXP. 1.--In 1877 chrysalides of _P. Ajax_ and _Grapta Interrogationis_
(the eggs laid by females of the form _Fabricii_) were experimented
upon; but the results were not satisfactory, for the reason that the
author having been absent from home most of the time while the pupæ
were in the ice-box, on his return found the temperature above 5°-6°
R. And so far as could be told, the ice had been put in irregularly,
and there might have been intervals during which no ice at all was in
the box. Six chrysalides of the _Grapta_ so exposed produced unchanged
_Umbrosa_, the co-form with _Fabricii_. But all chrysalides from the
same lot of eggs, and not exposed to cold, also produced _Umbrosa_.
Nothing was learnt, therefore, respecting this species.
But chrysalides of _Ajax_, exposed at same time, did give changed
butterflies to some extent. From a lot of 8, placed in the box when
under twelve hours from pupation, and left for twenty-four days,
there came 5 males and 3 females. Of these was 1 _Telamonides_ in
markings and coloration, and all the rest were between _Marcellus_ and
_Telamonides_. Two other chrysalides on ice for twenty-three days gave
_Telamonides_, but 3 more exposed twenty-six days, and all one hour old
when put on ice, were unchanged, producing _Marcellus_.
During the same season 6 other _Ajax_ chrysalides were placed in the
box, and kept at about 0°-1° R. One was one hour old, and remained
for five days; 1 was one hour old, and remained for two days and
three-quarters; 3 at three hours old for eight days; and 1 (age
omitted), six days. All these gave unchanged butterflies of the form
_Marcellus_.
EXP. 2.--In May, 1878, many chrysalides were placed in the ice-box,
being from eggs laid by _Ajax_, var. _Walshii_. The youngest were
but ten to fifteen minutes from pupation, and were soft; others at
intervals up to twenty-four hours (the chrysalis is hard at about
twelve hours); after that, each day up to eight days after pupation.
All were removed from the box on the same day, 28th May. The exposure
was from nineteen to five days, those chrysalides which were put on ice
latest having the shortest exposure. The author wished to determine if
possible whether, in order to effect any change, it was necessary that
cold should be applied immediately after pupation or if one or several
days might intervene between pupation and refrigeration. Inasmuch as no
colour begins to show itself in the pupæ till a few hours, or at most
a day or two, before the butterfly emerges, it was thought possible
that cold applied shortly before that time would be quite as effective
as if applied earlier and especially very soon after pupation. The
result was, that more than half of the chrysalides exposed before they
had hardened died: 1 exposed at ten minutes, 2 at one hour, 1 at two
hours, 2 at three hours after pupation. On the other hand 1 at fifteen
minutes produced a butterfly, 1 at two hours, another at twelve hours.
The temperature was from 0°-1° R. most of the time, but varied somewhat
each day as the ice melted. The normal chrysalis period is from eleven
to fourteen days, in case the butterfly emerges the same season, but
very rarely an individual will emerge several weeks after pupation.
On the 14th day after taking the pupæ from the ice, 1 _Telamonides_
emerged from a chrysalis which had been placed in the ice-box
three days after pupation, and was on ice sixteen days.
On 19th day, 1 _Telamonides_ emerged from a pupa put on the ice
twelve hours after pupation, and kept there eleven days.
On 19th day, 1 _Walshii_ emerged from a pupa two hours old, and on
ice eleven days.
All the rest emerged _Marcellus_, unchanged, but at periods prolonged
in a surprising way.
1 on 43rd day exposed 15 minutes after pupation.
” 46th ” 2 hours ”
” 53rd ” 24 hours ”
” 62nd ” 6 days ”
” 63rd ” 4 days ”
” 66th ” 7 days ”
” 77th ” 4 days ”
” 81st ” 12 hours ”
” 91st ” 5 days ”
” 96th ” 19 hours ”
Five chrysalides lived through the winter, and all gave _Telamonides_
in the spring of 1879.
It appeared, therefore, that the only effect produced by cold in all
chrysalides exposed more than three days after pupation was to retard
the emergence of the butterfly. But even in some of these earliest
exposed, and kept on the ice for full nineteen days, the only effect
seemed to be to retard the butterfly.
EXP. 3.--In June, 1879, eggs of the form _Marcellus_ were obtained, and
in due time gave 104 chrysalides. Of these one-third were placed in the
ice-box at from twelve to twenty-four hours after pupation, and were
divided into 3 lots.
1st, 9 pupæ, kept on ice 14 days.
2nd, 12 ” ” 20 days.
3rd, 11 ” ” 25 days.
Temperature 0°-1° R. most of the time, but varying somewhat as the ice
melted. (Both in 1878 and 1879 Mr. Edwards watched the box himself, and
endeavoured to keep a low temperature.)
Of the 69 chrysalides not exposed to cold, 34 gave butterflies at from
eleven to fourteen days after pupation, and 1 additional male emerged
11th August, or twenty-two days at least past the regular period of the
species.
Of the iced chrysalides, from lot No. 1 emerged 4 females at eight days
and a half to nine days and a half after removal from the ice, and 5
are now alive (Nov. 18) and will go over the winter.
From lot No. 2 emerged 1 male and 5 females at eight to nine days;
another male came out at forty days; and 5 will hibernate.
From lot No. 3 emerged 4 females at nine to twelve days; another male
came out at fifty-four days; and 6 were found to be dead.
In this experiment the author wished to see as exactly as
possible--First, in what points changes would occur. Second, if there
would be any change in the shape of the wings, as well as in markings
or coloration--that is, whether the shape might remain as that of
_Marcellus_, while the markings might be of _Telamonides_ or _Walshii_;
a summer form with winter markings. Third, to ascertain more closely
than had yet been done what length of exposure was required to bring
about a decided change, and what would be the effect of prolonging
this period. After the experiments with _Phyciodes Tharos_, which had
resulted in a suffusion of colour, the author hoped that some similar
cases might be seen in _Ajax_. The decided changes in 1878 had been
produced by eleven and sixteen days’ cold. In 1877, an exposure of two
days and three-quarters to eight days had failed to produce an effect.
From these chrysalides 11 perfect butterflies were obtained, 1 male and
10 females. Some emerged crippled, and these were rejected, as it was
not possible to make out the markings satisfactorily.