Article beginning on page 420.
Psyche 5:420-422, 1888.

Full text (searchable PDF)
Durable link: http://psyche.entclub.org/5/5-420.html

The following unprocessed text is extracted from the PDF file, and is likely to be both incomplete and full of errors. Please consult the PDF file for the complete article.

420 PSYCHE. [November-December 1%.
ground. The duration of the larval days. stages was as follows .- 1st stage, 5
FOOD-PLANTS : Hamamelisvir-
days ; 2nd stage, 6
days ; 3rd stage, 6
ginica, Vaccinium stamineum.
days, 4th stage, 7 days; 5th stage, 7
Larvae from Ulster Co., N. Y.
THE NUMBER OF MOLTS OF LEPIDOPTEROUS LARVAE. BY HARRISON G. DYAR, RHINEBECK, N. Y.
Two articles have already appeared in
PSYCHE on this subject * and it is evi-
dent from a perusal of them that con-
siderable confusion exists as to the
number of molts of certain species.
In this article I propose to establish a criterion by -which different observa-
tions may be compared and errors de-
tected, for it is no difficult thing to
overlook a molt or even to think one
has occurred when it has not.
It will be seen by an examination of
the following figures that the widths of the head of a larva in its successive
'stages follow a regular geometrical pro- gression, and if, in examining the meas- urements of heads taken in following
out a life history, any deviation from
the calculated progression is shown,
it is evidence that an error has been
committed or that the larva has be-
haved in an abnormal manner ; but the
latter case can readily be distinguished from the former if a moderate degree of
care has been exercised in taking the
measurements. Hence, if two sets of
observations show a different number
of stages for the same insect but each
W. H. Edwards, Psyche, v. 3, p. 159.
A. K. Dimmock, Psyche, v. 5, p. as.
follows its own progression. we may
conclude that this variation is actual;
but if either set shows a lack of regular progression that one we must regard
with suspicion. Corroborative observa-
tions of the kind indicated are to be de- sired and until we have them we can
not speak with confidence about the
number of molts of any species.
I
recommend that all who hereafter de-
scribe larval stages give the width of
the head for each stage. I have selected the head as the part not subject to
growth during the stage, and its width
as the most convenient measurement to
take.
In the following I give first the calcu- lated widths of head under each species, with the ratio, followed by those that
were actually found. All measurements
are in millimeters and may be con-
sidered accurate to within . I mm. Cer-
tain irregularities are commented upon
in the notes to which the small num-
bers refer.
FOUR STAGES.
Callosamia fromethea Drury. calc. I .I
1.6 2.3 3.3, r .yo
found 1.0 1.7 2.3 3.3




================================================================================

November-December 1890.1
PSYCHE. 421
FIVE STAGES.
Papilio cresphontes Cram. cdc. .7 I. I
1.6 2.3 3.4, r -68
found .6 1.1 1.6 2.2 3.4
Eudamus tiwus, Fabr. calc. .6 I .o 1.7
found
. 6 1.1 1.8 2.j2-
t --
1.7 3.2 4.7
Synto~neida epilais, Walk. calc. .6
Datana drexeiii Hy. Edw. calc. .6 I. I
1.9 3.2 5.4, r -60
found .5 1.1 1.7-1.9 3.2 5.4
Datum major G. & R. calc. .6 1.0 1.8
3.1 5.3, r -58
found .5 1.1 1.7 3.1 5.3
Datana Palmii Bent. calc. .5 .9 1.5
2.7 4.6, r -58.
' found.5.9 1.62.74.6
Datanu intege~v-/ma G. & R. calc. -5
.9 1.6 2.6 4.3, 1- '60
found - .9 1.6 2.7 4.3.
Datmza $erspic?iu G. & R. calc .7 I .I
1.7 2.7 4.1, r -65
found .5 1.1 1.6-8 2.7 4.1
Oedemasia concinna A. & S. calc. .45
Schi'zura leptinoides Grote calc. .5 .S
1.3 2.1 3.3, r -64
found .5 .8 1.5 2. I 3.3
Schizwa ipomeae Doubl. calc. .6 .Q I .4
2.2 3.3, r -66
1.3 2.0 3.2, r 64.
found .4 .7 1.35 2.1 3.2
Piatysamia cecrojia Linn. calc. 1.1
1.3~ 1.6 2.4 3.5 5.5
found { I.I
----
SIX STAGES.
Euchaetes egie Harr. calc. .45 .6 .9
1.3 1.9 2.7, r .70
found- -6 .g 1.3 2.0 2 7
Edema albifrons S. & A. calc. .4 .6
1.0 1.7 2.7 4.3, r -62
. .7 1.3 1.7 2.3 -
found
å´ -7 1.3 1.7 2.2 3.2
Dryopteris rosea Walk. calc. .25 .4
. -
found .3 .4 .6 9. 1.3 2.2
Hy$erchi?-ia io Fabr. calc. .8 I. I I .7 2.4 3.5 5.1, r -69
found .S 1.2 1.7 2.6 3.4 5.1
Clisiocam$a americana Har. calc. .4
found {
. .6 - - - -
- - .9 1.3 2.0 3.0
A~otis incivis Guen. calc, .4 .6 .9 1.3
SEVEN STAGES.
Halisidota harrisii Walsh. calc. .4 .6
-8 1.2 1.7 2.4 3.5, r -70
foilnd <
. .6 .9 1.4 1.6 2.3 3.5
.4 -6 - I .3 1.7 2.6 3.6
Hyphantria cunea Drury. calc. .3 .4
.6 .8 1.2 1.7 2.4, r .70
found - - 1.5 2.2 3.36
Oryyia definita Pack. ? calc. .s .7 1.0
Heterocampa subrotata Ham. calc. 1.4 2.0 2.8 4.0, r .70 .7 1.1 1.7 2.6 3.9, r.66
found - .7 I .o I .5 2. I 2.8 3.5 l1
found .6 1.1 1.7 2.6 3.8
EIGHT STAGES.
Heterocampa unicolor Pack. calc. .5 .8
Scefsis edivard&Grote. calc. .3 .4 .6




================================================================================

~CH,??. [November-December 1890.
.9 1.2 1.6 2.2 3.0, r .73
( .4 .5 .7 -9 -1.2 1.6 -
-
found) '
I ---
.9 I .z 1.6 2.3
L 3-0
NINE STAGES.
Hal/sido/a caryae Harr. calc. .5 .7 .g
1.2 1.6 2.0 2.6 3.4 4.3, r -78
found .4 .6 -I2 1.2 1.5 3.1 3.7
3-4 4-4
Halisidota tesselaris S. & A. calc. .5
.7 .9 1.2 1.6 2,o 2.6 3.4
4.3, r. 7s
(___ _ 1.3 1.7 -I2
found I "7 3.5 4.3
.4 .6 .9 - 1.6 2.1 3.6
TEN STAGES.
.P~wrha?*ctia isabella A. & S. calc. .4 .5 .7 .9 1.1 1.6 2.0 2.6 3.2
4.1, I- 979
found .4 .5 .7 .9 1.2 1.6 2.2 2.6
3.6 ls 4.1
NOTES.
It will be seen that I corroborate the obser- vations of Mr. W. H. Edwards in giving four stages to this species, and as my specimens were bred in Rhinebeck, N. Y. the theory of variation in the number of molts due to climat- ic influence suggested by Mrs. Dimmock
(Psyche, v. 5. p. 29) does not appear to be sustained.
This measurement, 2.5 mm., is too small
as the larva was unable to cast its skin and the head was dwarfed.
This is too large; it is possibly an error of observation and was not verified.
An incorrect measurement. I find it
marked with an (?) in my notes.
A remarkable instance of excessive de-
velopment. I do not think any error was
made. The second example behaved in a
normal manner as can be seen from what
measurements I have.
My observations do not agree with those
of Dr. Packard on this species, who finds six stages. (Proc. Bost. soc. nat. hist. v. 24, p. 534-1
The second example has the normal meas-
urement.
Possibly I have made an error in
the first measurement.
It will be seen that in both examples no series is followed, but both larvae became unhealthy and died in the fifth and sixth stages respectively which probably accounts fur the dwarfed dimensions of their heads. This is one of the instances of abnormal de-
velopment which is readily distinguishable from an error of omission.
For examples of the latter see note (I2). In giving six stages to this species I cor- roborate the observations of Mr. Beuten- muller (Ent. Amer., v. 6, p. 75) but disagree with Dr. Packard who finds but five stages. (Proc. Bost. soc. nat. hist., v. 24, p. 525.) An erroneous measurement.
It is marked
in my notes as carelessly taken.
This larva died in the sixth stage and its head is seen to have been dwarfed.
l1 The last stage, width of head 3.5 mm., occurs only in larvae that produce female moths and it is seen to be too small for the series. I intend to make more observations on this species and will not comment on it further at this time.
l2 Examples of accidental omissions which were not detected at the time and which would have gone entirely unrecognized had it not been for the measurements recorded. On
making calculations and observing the ap- parent omissions I endeavored to obtain more larvae. No young caryae were to be had,
but some fesselaris, carefully watched ex- hibited the missing stage as may be seen from the second example.
l3 Probably an error. I found this larva very difficult to measure and this particular stage was not verified by measuring the cast head as most of the others were.




================================================================================