Later, the word heliotropism came to mean both the bending and the explanation of the process. One of the most recent papers on this subject is by Peterson and Haeussler (74), who studied the reactions of the Oriental fruit moth (Laspeyresia molesta Busck) and codling moth {Carpocapsa pomponellaL.) in and 1927.
PHOTOTACTIC EXPERIMENTS ON CODLING-MOTH LARVAE The writer, like other observers, has found the adult codling moth
In bright light, although not in direct sunlight, the first instar codling moth larvae were found to be weakly photopositive, and their responses were similar in general principles to those described by other investigators. First-instar larvae, confined in an uncovered box in which most light was reflected from the ceiling, moved in all directions.
CHEMOTAXIS
Lammert does not support this hypothesis because he failed to find a migration of pigment in the ocelli of certain insects, but his tests in which the ocelli became black led him to believe that lepidopterous larvae have two types of photoreceptors— the ocelli and others lying in the body integument. The present writer's few experiments on this subject do not indicate that codling moth larvae have photoreceptors in their integument, and these larvae do not appear to be suitable material for looking for a migration of pigment in their ocelli.
REVIEW OF LITERATURE
CHEMOTACTIC EXPERIMENTS ON CODLING-MOTH LARVAE The preliminary results which follow were obtained by testing
As an example of the procedure in the tests, newly hatched larvae are placed in the phototactic box described on page 12 to ensure that they responded normally to light. The caterpillar was then placed inside the circle and allowed to search for the apple pieces while slowly moving towards the light. Several larvae that had recently hatched went to the apple pieces in an average of 65 percent of their chances; several larvae.
Several newly hatched larvae went to the cork pieces in 40 percent of the opportunities presented to them, and others went in over the squares. Since first instar larvae have photopositive eyes, they therefore remain in the open air on the foliage of apple trees. and search for food freely, apparently unaided by their senses to within a few millimeters of the food, because they wandered in these tests. Pieces of cork, after being immersed in concentrated synthetic apple oil, were placed in the circle and within moments the oil had spread onto the paper surrounding the cork.
The next day, the same pieces of cork were tested with another recently hatched larva.
GEOTAXIS
GEOTACTIC EXPERIMENTS ON CODLING-MOTH LARVAE Recently hatched codling-moth larvae do not seem to be influenced
At the extreme top and bottom of the branch, string was loosely wrapped around the twigs to create a cocoon site for the larvae tested. After the phototactic test, a larva was placed horizontally in one of the forks of the branch, and in such a position the light was not a disturbing factor. The individuals who were weakly photonegative or indifferent to light were generally not ready for it.
This shows that the sixth instar larvae at the time of cocooning are strongly geopositive, but shortly before they were normally indifferent to gravity. As they ascended the branch, a few of the caterpillars seemed to perceive the small apple when within an inch of it. They stopped crawling and reached as far as possible towards the apple.
THIGMOTAXIS
TIIIGMOTACTIC EXPERIMENTS ON CODLING-MOTH LARVAE All instars of the codling moth seem to have a well-developed sense
When they are ready to roll, these larvae prefer a narrow, dark place in which they crawl, but they are not dark, they do not hesitate to roll in a well-lit place. Larvae easily spin on these sticks, which can later be transferred to other containers. Another practical application of the thigmopositive and photonegative reactions of these larvae has been used for many years.
When we place tapes around the trunk of apple trees, which serve as an additional method of suppression, we are only taking advantage of natural laws. Therefore, as far as tropic responses are concerned, the vulnerable period in the larval life history of the tropic moth appears to be due to a change in tropisms.
Tropic Receptors
PHOTORECEPTORS
Judging from sections through the eyes of adults and larvae of this moth, the photoreceptors appear to be normally developed, but since so much work has already been done on the morphology of the eyes of insect no. Therefore, he believes that these larvae have a light-sensitive skin that can be compared. The results obtained by Durken (13) bear indirectly on the subject of body pigment being used to direct larval movements.
He spent five years experimenting to determine the effects of colored lights on the developing stages of the cabbage butterfly. Glass panes of vivaria were painted white and the effect of reflected light from green food on the caterpillars was observed. Pigmentation of images was completely unaffected by darkness or light, and was absolutely independent of that of the pupae.
CHEMORECEPTORS
SO-CALLED OLFACTORY ORGANS
- SO-CALLED TASTE ORGANS
Accepting that the pit pins and terminal pins are the only olfactory organs of Lepidoptera, and drawing conclusions from the observations of Schenk and the present writer, eight individuals (table 2, nos. i to 34 specimens examined cannot smell at all, the present writer (50 , 51) made a thorough study of their disposition and structure in .. many lepidoptera and their larvae Figures 6 to 8 represent the internal structure and innervation of the sensory pores and hairs, as well as the internal anatomy of the arms and legs where there are pores on them.
The arrows, /, 3, andj, represent the positions in which the butterflies were tested, the position of the walking legs being indicated by the cross bars. According to these results, almost half of the olfactory receptors must be located somewhere other than on the antennae. In the higher animals the olfactory organs. fig. 12) is separated from the outside air only by a thin, watery layer of mucus, and recent results show that the free ends of the olfactory cilia actually come into contact with the air.
The so-called taste organs of Lepidoptera consist, according to Degener's review (see Schroder (80) p. 149), of two round groups of sensory hairs on the underside of the pharynx.
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ON THE TROPISM OF LEPIDOPTERA McINDOO 37 with the four middle and hind legs touching the wire screen, and with the antennae lying directly on the cheesecloth moistened with apple juice. Hutterfly was then held in position 2; i.e., with the head and antennae just moistened with distilled water and with the metatarsals resting on this wet cloth. If the insect reacted at all in this position, the response was either an odor or a response elicited by foot contact on the cloth, or the response was a combination of olfactory and contact stimuli.
In this position, the insect always responded and the responses were of the same type but different in degree from those in position 2. In order to accurately compare the results obtained, the first four substances were used based on their molecular weights. Butterflies could distinguish a sugar solution from a solution of hydrochloric acid and quinine or from distilled water with just their feet.
Alinnich believes that these organs lie in the distal end of the first joint, and mainly in the other four joints.
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- AUDIRECEPTORS
- TYMPANIC ORGANS
- CHORDOTONAL ORGANS
- JOHNSTON ORGANS
- AUDITORY HAIRS
- THIGMORECEPTORS
- TACTILE ORGANS
- GEORECEPTORS
- BALANCING ORGANS
- OTHER RECEPTORS
When the eardrums (fig. 13, A, T) of both eardrums were destroyed, the moths no longer responded to sounds. In both sexes of the codling moth the present writer found the Johnston organs (fig. 14) highly developed, and the sense rod. Eggers informs us that their structure is not correlated with that of the eardrums.
Eggers believes they probably sense the movements of the joint membrane to which they were attached. Recently, Minnich (64) has revived the subject of auditory hairs and has shown beyond doubt that certain hairs are sound receivers in the larvae of the mourning cloak butterfly. Most of the tactile hairs on the wings appeared to be ordinary sensory hairs (Fig. 4, A,St), but some sensory scales were seen (Ssq).
Some of the tactile hairs on the antennae and mouth parts of moth larvae are shown in Figures 9 and 10.
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Scent-Producing Organs
In female passion fruit butterflies, a pair of shaped knobs on the back of the abdomen serve as the scent-producing organ. This organ is a pair of invaginated and strongly wrinkled sacs at the posterior end of the abdomen. No one seems to have yet described an odor-producing organ like that of the beaked moth, but Freiling (23) described a similar one in the male butterfly (Daiiais scptcntrionalis).
The scent hairs are filled with a matrix substance and the secretion exits through small pores in the walls of the hairs. To shed light on the biology of the codling moth, a thorough study of the tropisms of this insect was begun in the spring of 1927. In adults they are found on the wings, legs, mouthparts and the second segment of the antennae.
The only one found in the thigh moth is a pair of invaginated sacs.
LITERATURE CITED
Of these four, the writer found only Johnston's organs in the adult grasshopper, but Graber in 1882 saw chordotonal organs in the larva of the grasshopper. Other special sensory receptors of the rugose include some innervated hairs used as tactile organs and a well-developed structure in thelabialpalpus. Speed of movement in Vaiiessa antiopa in intermittent and continuous light of different illuminations and its bearing on the "continuous action theory" of orientation.
On stridulation in certain Lepidoptera, and on the deformation of the hindwings in the males of certain Ommalophorinae. Note on the specific secondary sexual character found in the Geometridae at the sensory organ located at the base of the abdomen. On the comb-bearing flap present on the fourth abdominal segment in the males of certain Notodontidae.
A quantitative study of tarsal sensitivity to sucrose solutions in the red admiral butterfly, Pyrameisatalanta Linn.
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