H. B. Weiss.
Thermal Conductivity of Cocoons.
Psyche 21(1):45-50, 1914.

This article at Hindawi Publishing: https://doi.org/10.1155/1914/73975
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Alexander-Neotropical Hexatomini
Pu&e 21:45-50 (1914). hup ttpsychu einclub orgt21t21-045 html



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19141 Weiss-Thermal Conductivity of Cocoons 45 Rostrum and palpi brown; scape of antenna light yellowish-brown, the basal segment slightly darker than the second segment; flagellum broken. Front,
vertex and occiput dark-colored, thickly bluish-grey pruinose. Frontal tubercle prominent, not notched.
Mesonotum yellowish-brown, shiny, a narrow deep brown line on either side of the broad dorsal median portion, beginning above the pseudosutural region, nar- rowing behind and ending before the transverse suture: a large rounded brown spot on the sides of the sclerite before the transverse suture; scutum, scutellum and postnotum yellowish-brown with a faint greyish bloom; a rounded darker brown spot on the lateral lobes of the latter. Pleurae very light yellow, a large rounded brown spot on the mesopleurae underneath the wing-root and less distinct spots on the propleurse and cervical sclerites forming an interrupted dorso-pleurat band. Halteres deep brown.
Legs: coxae and trochanters light yellow; femora yellowish-brown, extreme tip darker brown; tibiae brown; fore metatarsus brown on basal two-fifths, remaining portions of fore tarsi pure white except the last segment which is brownish; middle leg, with the basal third of the metatarsus. brown; metatarsus of the hind legs entirely white. Wings: subhyaline or slightly tinged with darker, especially toward the tip; veins dark brown. Venation, see figure 2.
Abdominal tergum with the segments dark brown; segment 1 pallid at base, darker apically; extreme margin of segments 2-6 pallid; 7-8, not pale at tip; c? hypopygium reddish-brown; sternites dull yellow. Holotype, 8. Patalue, Guatemala, Central America. 700 ft. (Dr. G. Eisen.) Allotype, 9, with the type. Received at the National Museum, January 6, 1903. Type in U. S. Nat. Mus. Coll.; allotype in author's collection. EXPLANATION OF PLATE IV.
The figures are all drawn to scale by means of a projection microscope. Fig. 1. Eriocera kaieturensis sp. nov.; wing. Fig. 2. Penthoptera conjuncta sp. nov.; wing. Fig. 3. Eriocera cornigera sp. nov.; wing. Fig. 4. Eriocera macrocera sp. nov.; wing. Fig. 5. Eriocera peruviana sp. nov.; wing. Fig. 6. Eriocera longistyla Alex; wing.
Fig. 7. Eriocera magnified sp. nov.; wing. Fig. 8. Eriocera perpulchra sp. nov.; wing. THERMAL CONDUCTIVITY OF COCOONS.
BY HARRY B. WEISS,
New ~runiwick, N. J.
With a view toward determining the value of cocoons as a pi- tection against extremes of temperature, thermometric tests of those of quite a number of species were made in the following man- ner: Normal empty cocoons were selected and the bulbs of ther- -



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4 6 Psyche [February
mometers placed inside so as to occupy as nearly as possible the positions of the pupse, that is, care was taken to have an air space surrounding each bulb. Each cocoon was fastened in place by elastic bands and then glued or sealed with wax. The following tables show three different sets of conditions: one under normal field temperatures, one where a gradual rise takes place effected by placing the cocoon in an electric oven, and the other where a sudden drop occurs. The average length of time for the temperature of the inside of the cocoon to reach that of the surrounding atmosphere during a rise and fall was almost three quarters of an hour.
Cocoon of Telea polyphemus.
Field Conditions.
Outside
temperature.
10å¡C
8' -
7'
Surrounding
temperature.
48'C.
' 51'
55'
57'
60å
61'
62'
Surrounding
temperature.
10å¡C
2'
0'
0'
0'
Outside
temperature.
10å¡C
9'
7'
Gradual Rise.
Time.
0 min.
10 "
20 '<
25 "
30 "
35 <'
40 "
Sudden Drop.
Time.
0 min.
5 "
15 "
25 "
35 <'
Cocoon of Bombyx mori.
Field Conditions.
Temperature
inside cocoon.
15'C
12'
10'
Temperature
inside cocoon.
48' C.
48'
54'
55O
57'
59O
62'
Temperature
inside cocoon.
14'C.
14'
10'
6'
4 '
Temperature
inside cocoon.
15'C
12'
11'




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3141 Weiss~Thermal Conductivity of Cocoons Surrounding
temperature.
o0c.
44O
61å
66:
68'
75O
Gradual Rise.
Time. Temperature
inside cocoon.
0 min. 6OC.
10 '< 37O
20 " 54O
30 <' 58O
40 " 64O
50 " 75O
Sudden Drop.
Surrounding Time. Temperature
temperature. inside cocoon.
10å¡C 0 min. 14OC.
O0 5 " 14O
O0 15 " lo0
O0 25 " 8'
o0 35 " 5O
Bag of Thyridopteryx ephemerceformis.
Field Conditions.
Outside Temperature
temperature. inside bag.
Bå¡C 13OC.
7O 11å
7O 7O
Surrounding
temperature
26OC.
38'
48'
50å
53
55O
56"
Gradual Rise.
Time.
0 min.
10 ''
20 "
25 "
30 "
35 ''
40 "
Temperature
inside bag.
26OC.
29'
42'
43O
48'
52'
53O
Sudden Drop.
'Surrounding Time. Temperature a
temperature.
inside bag.
10å¡C 0 min. 26OC.
O0 5 " 25O
O0 15 " 13"
O0 25 " 5'
O0 35 " 3O




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48 Psyche [February
Cocoons of Callosamia promethea and Tropoea luna gave similar results. In spite of errors due to imperfect conditions, these tables show that the temperature inside a cocoon is practically the same as that of the surrounding air and that there is a constant tend- ency for the inside temperature to approach that of its surround- ings.
One fact, however, which is readily apparent, is that sudden changes of temperature do not occur within the cocoon. When the outside temperature was suddenly lowered as from 10å¡C to Oå¡C. the temperatures in the cocoons fell gradually and even dur- ing a gradual rise, the cocoon temperature lagged behind that of its surroundings. This is no doubt due to the poor conducting qualities of air and. silk.
As the cocoon of Samia cecropia is double and the pupa thereby protected by two air spaces, this was somewhat more resistant to sudden changes of temperature than the others, a longer time being required for the inside temperature to reach that of the at- mosphere, when either a rise or fall occurred. From figures showing comparative conductivity1 one can see that air is extremely poor conductor, and also wool, the thermal conductivity of which approaches that of silk, the exact figures for silk being unobtainable. It is worth noting that the rather thin paper-like covering of the bag worm was equally as resistant to sudden changes, as the well made heavier cocoons of Bombyx mori and Callosamia promethea.
From the standpoint of temperature alone it is doubtful if the pupa needs the protection afforded by a thick cocoon, especially when we consider that pup= of the superfamily Papilionoidea are without such coverings.
From the standpoint, of moisture however, it is exceedingly necessary for the insect to have such a covering, especially if the pupal stage is passed on the ground among leaves or in situations likely to be moist.
Cocoons of Callosamia promethea, the layers of which tend to fray out toward the proximal ends, which are not finished inside with coatings similar to the remainder of the interiors, when partly ^-The conductivities for heat of a number of substances is as follows: Copper, 1.041, Iron 0.167, Ice 0.0057, Marble 0.005, Glass 0.0025, Cork 0.0007, Wool 0.00012, Paper 0.000094, Air 0.0000563




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19141 Weiss~Thermal Conductivity of Cocoons 49 submerged in water for seven hours, showed interiors perfectly dry, the water having penetrated only the outer layer. Those partly submerged in alcohol and sulphuric acid for the same time were wet clear through, the acid having softened the entire mass. Alcohol penetrated easily but did not have the disintegrating action of the acid. When totally submerged in the above liquids for one hour, the acid and alcohol readily entered the proximal end from which the moth escapes and also penetrated the sides, but water was effectually kept out, the fringe-like ends of the layers being bunched together sufficiently for that purpose, and the pressure of the air inside the cocoon undoubtedly helping also. It is a generally accepted fact that the interiors of cocoons are coated all over with a gummy resinous substance, also that the emergence is usually effected by a fluid secreted by the insect, which has the property of softening the threads and gum. The following paragraphs from Trouvelot explain how this is accomplished :
" T. polyphemus is provided with two glands opening into the mouth, which secrete during the last few days of the pupa state, a fluid which is a dissolvent for the gum so firmly uniting the fibres of the cocoon.
"This liquid is composed in great part of bombycic acid. When
the insect has accomplished the work of transformation, which is going on under the pupa skin, it manifests a great activity, and soon the chrysalis covering bursts open longitudinally upon the thorax; the head and legs are soon disengaged, and the acid flows from its mouth, wetting the inside of the cocoon. The process of exclusion from the cocoon lasts for as much as half an hour. The insect seems to be instinctively aware that some time is required to dissolve the gum, as it does not make any attempt to open the the fibres and seems to wait with patience this event. When the liquid has fully penetrated the cocoon, the pupa contracts its body, and pressing the hinder end, which is furnished with little hooks against the inside of the cocoon, forcibly extends its body; at the same time the head pushes hard upon the fibres and a little swelling is observed on the outside.
"These contractions and extensions of the body are repeated many times and more fluid is added to soften the gum, until under these efforts the cocoon swells and finally the fibres separate, and



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