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==Ultraviolet Light and Butterfly Mating Behavior== |
==Ultraviolet Light and Butterfly Mating Behavior== |
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[[Image:White Cabbage Butterfly Cartoon.jpg|thumb|right| Drawings of the White Cabbage Butterfly representing the butterfly under UV light and the visible region of light.]] |
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White Cabbage Butterflies, ''[[pieris rapae]] crucivora'', use their secret ultraviolet communication system to initiate mating behavior. In this species, ultraviolet reflection is sexually dimorphic with females exhibiting the ability to reflect ultraviolet light of 380 nm to 400 nm and males being less able to reflect UV. Males who perceive an ultraviolet reflection from a female initiate a courtship behavior that involves approaching the female and attempting to copulate. Females communicate their receptivity to males using their ultraviolet communication system. The ultraviolet reflectance is thought to be concentrated to the ventral side of a female’s hind wing. This was determined experimentally by comparing the number of approaches to different parts of butterfly wings. The results showed that the female’s ventral hind wing was the greatest releaser of male sexual behavior.<ref>Obara Y. and Hidaka, T. (1968): “Recognition of the Female by the Male, on the basis of Ultra-Violet reflection, in the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Proc. Japan Acad. Vol. 44 No. 8 ppg 828-832.</ref> Although ultraviolet reflectance releases the sexual behavior, the strongest reflection of UV light is not the strongest releaser for the behavior. As a result, male white cabbage butterflies must have a preference for a certain level of UV reflectance from females.<ref>Obara Y. (1970): “Studies on the Mating Behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Z. vergl. Physiologie: 60, ppg 99-116.</ref> Using a private ultraviolet communication system, female White Cabbage Butterflies signal their receptivity and initiate male mating behavior. |
White Cabbage Butterflies, ''[[pieris rapae]] crucivora'', use their secret ultraviolet communication system to initiate mating behavior. In this species, ultraviolet reflection is sexually dimorphic with females exhibiting the ability to reflect ultraviolet light of 380 nm to 400 nm and males being less able to reflect UV. Males who perceive an ultraviolet reflection from a female initiate a courtship behavior that involves approaching the female and attempting to copulate. Females communicate their receptivity to males using their ultraviolet communication system. The ultraviolet reflectance is thought to be concentrated to the ventral side of a female’s hind wing. This was determined experimentally by comparing the number of approaches to different parts of butterfly wings. The results showed that the female’s ventral hind wing was the greatest releaser of male sexual behavior.<ref>Obara Y. and Hidaka, T. (1968): “Recognition of the Female by the Male, on the basis of Ultra-Violet reflection, in the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Proc. Japan Acad. Vol. 44 No. 8 ppg 828-832.</ref> Although ultraviolet reflectance releases the sexual behavior, the strongest reflection of UV light is not the strongest releaser for the behavior. As a result, male white cabbage butterflies must have a preference for a certain level of UV reflectance from females.<ref>Obara Y. (1970): “Studies on the Mating Behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Z. vergl. Physiologie: 60, ppg 99-116.</ref> Using a private ultraviolet communication system, female White Cabbage Butterflies signal their receptivity and initiate male mating behavior. |
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Ultraviolet light is not only an activator of male sexual behavior: Its absence may also stop an approaching male and his attempt to copulate. Female White Cabbage Butterflies are not always receptive to male White Cabbage Butterflies and to communicate this message, they assume the mate refusal posture. This behavior consists of opening the wings and straightening of the abdomen.<ref>Obara Y. (1970): “Studies on the Mating Behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Z. vergl. Physiologie: 60, ppg 99-116.</ref> Opening of the wings in this manner exposes the dorsal side of the female wings which are known to be unable to reflect ultraviolet light. In effect, females are removing the ultraviolet signal that initiates male sexual behavior, resulting in the abrupt halt of male sexual behavior. Female White Cabbage Butterflies take advantage of the personal butterfly ultraviolet communication system to also reject males by removing an ultraviolet reflectance signal. |
Ultraviolet light is not only an activator of male sexual behavior: Its absence may also stop an approaching male and his attempt to copulate. Female White Cabbage Butterflies are not always receptive to male White Cabbage Butterflies and to communicate this message, they assume the mate refusal posture. This behavior consists of opening the wings and straightening of the abdomen.<ref>Obara Y. (1970): “Studies on the Mating Behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Z. vergl. Physiologie: 60, ppg 99-116.</ref> Opening of the wings in this manner exposes the dorsal side of the female wings which are known to be unable to reflect ultraviolet light. In effect, females are removing the ultraviolet signal that initiates male sexual behavior, resulting in the abrupt halt of male sexual behavior. Female White Cabbage Butterflies take advantage of the personal butterfly ultraviolet communication system to also reject males by removing an ultraviolet reflectance signal. |
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==Ultraviolet Light and Butterfly Sex Recognition== |
==Ultraviolet Light and Butterfly Sex Recognition== |
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Revision as of 03:04, 7 December 2009
Ultraviolet Light and Butterfly Communication
Butterflies, or members of the Papilionoidea superfamily, are known for their beautiful displays on their wings. In the visible region of the electromagnetic spectrum, the only region available to most vertebrates for vision, two different species of butterflies can look remarkably similar or even identical. If used in mimicry, this attribute could afford a butterfly an advantage in evading predators, but it could also hinder their ability to visually find a conspecific mate. However, butterflies are able to access a part of the electromagnetic region for vision that most vertebrates and their predators cannot, the ultraviolet region that allows them to recognize conspecifics. The ultraviolet region is the part of the electromagnetic spectrum between 10 nm and 400 nm. Sensitivity to this region provides butterflies several benefits such as nectar guides for nectar, but it also affords them a private communication channel unavailable to predators. With this closed line transmitted by UV reflectance or absorbance and received by a unique photoreceptor, butterflies are able to facilitate mating behavior and sex recognition.
Ultraviolet Light Reflection and Absorption in Butterflies
One half of the private butterfly communication channel is the ability to send a signal either through UV reflectance or absorption via two separate means. The former is accomplished via structures on the wings’ scales and their systematic organization while the latter is achieved using pigments. The structural color’s mechanism has been elucidated through the study of the butterfly, Eurema lisa. In this particular insect, a small yellow portion of the dorsal surface of the wings is directionally UV reflectant. In other words, the image from the UV reflection can only be seen at a distinct range of angles from the point of origin. Through electron micrographs of these UV reflecting scales, it was determined that thin layer interference resulting from parallel ridges with six to seven flanges arranged systematically along the length of the scales caused UV reflection. In other words, the arrangement of the scales and ridges resulted in a maximal constructive interference with a wavelength in the ultraviolet region of the electromagnetic spectrum. This constructive interference is the UV reflectance seen by other butterflies.[1] The other ultraviolet signal in butterflies, absorbance, was determined to be governed by pigments called pterins. In wings containing this pigment, the wings are unable to reflect ultraviolet light as well as without the pigment because the pterins absorb the ultraviolet light.[2] Thus, butterflies are able to reflect ultraviolet light as a result of the organization and composition of their wing scales resulting in thin layer constructive interference and can absorb ultraviolet through the action of pterin pigments.
Ultraviolet Light Reception in Butterflies
The second half of the private butterfly communication channel is the ability to see an ultraviolet signal. The mechanism in perceiving ultraviolet light lies in the butterfly eye. The butterfly eye is similar to the average insect eye in that it is composed of numerous ommatidium. Each butterfly ommatidium contains nine photoreceptors with generally each photoreceptor utilizing a single visual pigment. A specific visual pigment is responsible for a butterfly’s ability to perceive UV light. The pigment responds maximally to ultraviolet light at approximately 350 nm and allows for the perception of ultraviolet light by butterflies.[3] Therefore, a visual pigment that responds to ultraviolet light is the mechanism behind ultraviolet light perception.
Ultraviolet Light and Butterfly Mating Behavior
White Cabbage Butterflies, pieris rapae crucivora, use their secret ultraviolet communication system to initiate mating behavior. In this species, ultraviolet reflection is sexually dimorphic with females exhibiting the ability to reflect ultraviolet light of 380 nm to 400 nm and males being less able to reflect UV. Males who perceive an ultraviolet reflection from a female initiate a courtship behavior that involves approaching the female and attempting to copulate. Females communicate their receptivity to males using their ultraviolet communication system. The ultraviolet reflectance is thought to be concentrated to the ventral side of a female’s hind wing. This was determined experimentally by comparing the number of approaches to different parts of butterfly wings. The results showed that the female’s ventral hind wing was the greatest releaser of male sexual behavior.[4] Although ultraviolet reflectance releases the sexual behavior, the strongest reflection of UV light is not the strongest releaser for the behavior. As a result, male white cabbage butterflies must have a preference for a certain level of UV reflectance from females.[5] Using a private ultraviolet communication system, female White Cabbage Butterflies signal their receptivity and initiate male mating behavior.
Ultraviolet light is not only an activator of male sexual behavior: Its absence may also stop an approaching male and his attempt to copulate. Female White Cabbage Butterflies are not always receptive to male White Cabbage Butterflies and to communicate this message, they assume the mate refusal posture. This behavior consists of opening the wings and straightening of the abdomen.[6] Opening of the wings in this manner exposes the dorsal side of the female wings which are known to be unable to reflect ultraviolet light. In effect, females are removing the ultraviolet signal that initiates male sexual behavior, resulting in the abrupt halt of male sexual behavior. Female White Cabbage Butterflies take advantage of the personal butterfly ultraviolet communication system to also reject males by removing an ultraviolet reflectance signal.
Ultraviolet Light and Butterfly Sex Recognition
Some butterfly species use ultraviolet light as a method of communicating sex. For example, in the species ''Eurema lisa'', males possess the structural requirements necessary to reflect ultraviolet light discussed previously, but females lack the ultraviolet light reflecting ridges. In both sexes of this species, a flutter response, or the rapid opening and closing of the wings, is performed when a male approaches another butterfly; yet, males copulate with females who perform this behavior, while retreating from males who perform the flutter response. By showing that male and female wings are similar in appearance except for UV reflectance and an approaching male is exposed to ultraviolet reflection of a male's wings during a flutter response, as well as ruling out temporal differences in the flutter behavior as a cause for sex recognition, Ronald Rutowski concluded that ultraviolet light was being used as an indicator of the male sex, thereby inhibiting male sexual behavior.[7] Eurema Lisa butterflies are one example of how butterflies can use the sexual dimorphism in UV reflectance to communicate sex.
The ultraviolet communication system employed by butterflies is also used an indicator of male sex to other rival males in the butterfly, Colias eurytheme. In this species, only males are able to reflect ultraviolet light off the dorsal side of their wings, while females cannot. The male sexual behavior is similar to most butterflies. The male hovers over a sitting female and dips to one of the female's sides and flutters. Then, if the female remains still, the male will land on her, her wings, or on the vegetation and attempt copulation. Copulation tends to last for an hour and often other males attempt to approach the mating pair. However, the male in midst of mating flashes his UV reflecting hind wings and approaching males are deterred. It was concluded that male Colias eurytheme uses ultraviolet light as a signal to repel other males.[8] Thus, male Colias eurtheme butterflies use their private channel in the ultraviolet to signal their sex as well as deter other males from copulating with their mates.
References
- ^ Ghiradella, H et al. (1972): “Ultraviolet Reflection of a Male Butterfly: Interference Color caused by Thin-Layer Elaboration of Wing Scales.” Science: 178, 4066,Ppg. 1214-1217.
- ^ Obara Y. et al. (2008): "Mate Preference in Males of the Cabbage Butterfly, Pieris rapae crucivora, Changes Seasonally with the Change in Female UV Color." Zoological Science 25, ppg 1-5.
- ^ Stavenga, Doekele G. and Arikawa, Kentaro. (2006): "Evolution of color and vision of butterflies." Arthropod Structure & Development 35, ppg 307-318.
- ^ Obara Y. and Hidaka, T. (1968): “Recognition of the Female by the Male, on the basis of Ultra-Violet reflection, in the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Proc. Japan Acad. Vol. 44 No. 8 ppg 828-832.
- ^ Obara Y. (1970): “Studies on the Mating Behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Z. vergl. Physiologie: 60, ppg 99-116.
- ^ Obara Y. (1970): “Studies on the Mating Behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Z. vergl. Physiologie: 60, ppg 99-116.
- ^ Rutowski, Ronald L. (1977): "The Use of Visual Cues in Sexual and Species Discrimination by Males of the Small Sulphur Butterfly Eurema Lisa (Lepidoptera, Pieridae). J. comp. Physiol. 115, ppg 61-74.
- ^ Silberglied, Robert E. and Taylor, Orley R. (1978): "Ultraviolet Reflection and Its Behavioral Role in the Courtship of the Sulfur Butterflies Colias eurytheme and C. philodice (Lepidoptera, Pieridae). Behav, Ecol. Sociobiol. 3, ppg. 203-243.