Spodoptera litura: Difference between revisions
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==== Morphology ==== |
==== Morphology ==== |
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There are slight differences in morphology between males and females. Male forewing length is 14-17 mm while female forewing length is slightly larger, measuring in at 15-18 mm. The orbicular spot on the forewing is also more pronounced in the males.<ref name=":11">{{Cite journal|date=2015-12-01|title=PM 7/124 (1) Spodoptera littoralis, Spodoptera litura, Spodoptera frugiperda, Spodoptera eridania|url=http://onlinelibrary.wiley.com/doi/10.1111/epp.12258/abstract|journal=EPPO Bulletin|language=en|volume=45|issue=3|pages=410–444|doi=10.1111/epp.12258|issn=1365-2338}}</ref> |
There are slight differences in morphology between males and females. Male forewing length is 14-17 mm while female forewing length is slightly larger, measuring in at 15-18 mm. The orbicular spot on the forewing is also more pronounced in the males.<ref name=":11">{{Cite journal|date=2015-12-01|title=PM 7/124 (1) Spodoptera littoralis, Spodoptera litura, Spodoptera frugiperda, Spodoptera eridania|url=http://onlinelibrary.wiley.com/doi/10.1111/epp.12258/abstract|journal=EPPO Bulletin|language=en|volume=45|issue=3|pages=410–444|doi=10.1111/epp.12258|issn=1365-2338}}</ref> |
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[[File:Spodoptera_litura_female.jpg|link=https://en.wikipedia.org/wiki/File:Spodoptera_litura_female.jpg|thumb|''Spodoptera litura'' female]] |
[[File:Spodoptera_litura_female.jpg|link=https://en.wikipedia.org/wiki/File:Spodoptera_litura_female.jpg|thumb|''Spodoptera litura'' female]] |
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=== Similar species === |
=== Similar species === |
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''Spodoptera litura'' and ''Spodoptera littoralis'' are very closely related species and discriminating between the two species can be difficult because the larvae and adult forms look quite similar. In fact, these two species are so similar that previous records that have claimed the presence of ''S. litura'' in areas such as Russia, Germany, and the UK may actually have been referring to ''S. littoralis''.<ref name=":2" /> Since both species are polyphagous, taking note of the host plant is not helpful in correct identification.<ref name=":6">{{Cite web|url=http://idtools.org/id/leps/lepintercept/pdfs/litura.pdf|title=NOCTUIDAE - Spodoptera litura (Fabricius)|last=|first=|date=|website=LepIntercept|archive-url=|archive-date=|dead-url=|access-date=October 1, 2017}}</ref> The only way to differentiate between the two is by inspecting their genitalia. In ''S. littoralis'', the ductus and ostium bursae are the same lengths while in ''S. litura'', they are of different lengths. In males, the juxta have characteristic shapes for each species.<ref name=":2" /> |
''Spodoptera litura'' and ''Spodoptera littoralis'' are very closely related species and discriminating between the two species can be difficult because the larvae and adult forms look quite similar. In fact, these two species are so similar that previous records that have claimed the presence of ''S. litura'' in areas such as Russia, Germany, and the UK may actually have been referring to ''S. littoralis''.<ref name=":2">{{Cite web|url=http://www.cabi.org/isc/datasheet/44520|title=Spodoptera litura (taro caterpillar)|website=www.cabi.org|access-date=2017-09-26}}</ref> Since both species are polyphagous, taking note of the host plant is not helpful in correct identification.<ref name=":6">{{Cite web|url=http://idtools.org/id/leps/lepintercept/pdfs/litura.pdf|title=NOCTUIDAE - Spodoptera litura (Fabricius)|last=|first=|date=|website=LepIntercept|archive-url=|archive-date=|dead-url=|access-date=October 1, 2017}}</ref> The only way to differentiate between the two is by inspecting their genitalia. In ''S. littoralis'', the ductus and ostium bursae are the same lengths while in ''S. litura'', they are of different lengths. In males, the juxta have characteristic shapes for each species.<ref name=":2" /> |
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== Range == |
== Range == |
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Revision as of 07:54, 2 October 2017
| Spodoptera litura | |
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| Spodoptera litura | |
| Scientific classification | |
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| Species: | S. litura
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| Binomial name | |
| Spodoptera litura (Fabricius, 1775)
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Spodoptera litura is a nocturnal species of moth in the Lepidoptera family. S. litura is best known as a serious polyphagous pest in Asia, Oceania and the Indian subcontinent.[1] Common names for this species include tobacco cutworm and cotton leafworm. These names reference two of the most common host plants of the moth. In total, 87 species of host plants that are parasitized by S. litura are of economic importance.[2] Its effects are quite disastrous, destroying economically important agricultural crops and decreasing yield in some plants completely.[3] Their potential impact on the many different cultivated crops, and subsequently the local agricultural economy, has led to efforts to control the pests.[4]
Description
Sex differences
Morphology
There are slight differences in morphology between males and females. Male forewing length is 14-17 mm while female forewing length is slightly larger, measuring in at 15-18 mm. The orbicular spot on the forewing is also more pronounced in the males.[5]
Food regulation
Regulation of macro nutrient input differs between males and females. Experimental results show that when presented with two nutritionally complementary diet options, one rich in protein and a second rich in carbohydrates, females tended to consume more protein than males while no differences in carbohydrates exist. Body utilization of the macro nutrients differed as well. Females were very efficient at converting the protein consumed into body growth and mass, reflecting the bodily requirements to produce eggs. Males, on the other hand, were more efficient at depositing lipid from ingested carbohydrates, possibly in preparation for migration.[6]
Similar species
Spodoptera litura and Spodoptera littoralis are very closely related species and discriminating between the two species can be difficult because the larvae and adult forms look quite similar. In fact, these two species are so similar that previous records that have claimed the presence of S. litura in areas such as Russia, Germany, and the UK may actually have been referring to S. littoralis.[7] Since both species are polyphagous, taking note of the host plant is not helpful in correct identification.[8] The only way to differentiate between the two is by inspecting their genitalia. In S. littoralis, the ductus and ostium bursae are the same lengths while in S. litura, they are of different lengths. In males, the juxta have characteristic shapes for each species.[7]
Range
S. litura is the most common in South Asia.[9] However, its natural range extends from the Oriental and Australasian areas to parts of the Palearctic areas as well.[5] The countries with the most widespread population of S. litura include but are not limited to China, Indonesia, India, Japan, and Malaysia.[2] The range of S. litura has also extended into non-indigenous regions through international trade. Moths in their egg or larvae stages can be present in soil, flower, or vegetation that are being transported across various regions.[7] S. litura has not been established in the United States of America yet except for the State of Hawaii.[2]
Habitat
This species of moths is a general herbivore and take residence on various plants.[10] As caterpillars, S. litura can only move short distances. However, adult moths can fly up to a distance of 1.5 km for a total duration of 4 hours. This helps disperse the moths into new habitats and onto different host plants as food sources are depleted.[7]
Life cycle
Although the length of a life cycle varies slightly throughout the different regions, a typical S. litura will complete 12 generations every year. Each generation lasts about a month, but temperature causes slight variations: life cycles in the winter tend to be slightly more than one month, while life cycles in the summer tend to be less than a full month.[7]
Egg
Eggs are spherical and slightly flattened. Each egg is around 0.6 mm in diameter with an orange-brown or pink color. These eggs are laid on the surface of leaves in big batches, with each cluster usually containing several hundred eggs. Females have a typical fecundity of 2000 to 2600 eggs.[7] However, experiments have shown that high temperatures and low humidity is inversely related to fecundity.[2] When laid, the egg batches are covered with hair scales provided by the female. This results in egg masses that are 4-7 mm in diameter and have a golden brown color due to the body hair coverings. Eggs will hatch 2-3 days after being laid.[7]
Larva
Larvae body length ranges from 2.3 to 32 mm. The larva is variable in color based on age. Younger larvae tend to be a lighter green while older ones develop to a dark green or brown color. A bright yellow stripe along the dorsal surface is a characteristic feature of the larvae. The larvae also has no hair at this stage. Newly hatched larvae can be found by looking for scratch marks on leaf surfaces. Since this S. litura is nocturnal, the larvae feed at night. During the day, they can usually be found in the soil around the plant. There are six instar stages, and by the last stage, the final instar can weigh up to 800 mg.[7]
Pupa
Pupation lasts around 7 to 10 days and takes place on the soil near the base of the plant. The pupa is typically 15-20 mm long, and its color is red-brown.[7] A characteristic feature is the presence of two small spines at the tip of the abdomen that are about 0.5 mm long each.[5]
Adult
Adult moths are on average 15-20 mm long and have a total wingspan of 30-38 mm. The body is a gray-brown color. The forewings are patterned with colors that consist of dark gray, red, and brown. The hindwings are grayish-white with a gray outline.[7] The mean female longevity is 8.3 days while for males it is 10.4 days.[11]
Mating
There is no mating activity on the first night of emergence as adults. Instead, the second night after emergence marks the maximum activity. Females mate an average of 3.1 times while the males have a mating average of 10.3. During copulation, males transfer amean of 1,052,640 sperm per mating.[11] Eggs during mating are laid in a cluster covered with hair from the female's abdomen. This acts as a protective layer from parasites predating on eggs.[12] Since S. litura is a nocturnal moth, all reproductive activities occur during the scotophase. This includes calling, courtship, mating, and oviposition. No mating occurs on the first night that the moth emerges. The second night, however, accounts for about 70% of the matings. Several studies have pointed out that the female lifespan decreases after mating. The reasons for this is still not fully known. Several possible explanations include physical injuries from the male genitalia or due to MAG secretions that make females commit more resources to reproduction instead of herself. [1] Specifics of MAG are discussed below.
Male accessory glands (MAG)
Male accessory glands, or MAG for short, is an reproductive evolutionary strategy adopted by males to gain higher fertilization. MAG contains many different kinds of molecules including carbohydrates, lipids, and proteins. When MAG is transferred from the male to the female during copulation, it exerts a wide range of effects on female post-mating behavior. Some of these effects include suppressing female receptivity to males, by reducing their sexual receptivity or sexual attractiveness. Experiments have shown that females exposed to MAG do not engage in mating call behavior the night they are exposed to the secretion. A successful mating that resulted in fertilized eggs led to an even longer break from sexual receptivity.[1]
Mating also has an effect on stimulating the egg production and ovulation. This phenomena may also be a result of the mechanical stimulation of male genitalia during copulation. However, studies have shown that MAG secretions are necessary for the maximum stimulation of the eggs. As a result, female longevity is negatively correlated with the number of eggs laid because a large portion of resources end up being used for the development of eggs.[1]
Pheromones
In sexually reproductive animals, this recognition and attraction of potential mates can occur in the form of pheromones.[13] In moth species, pheromones are produced by the females by pheromones glands and released to attract males of their species.[14] Accurate recognition of compatible mates is essential for reproductive success because failure to do so will come with steep costs: wasted time and energy, higher risk of predation, and reduction of viable offspring. Therefore, there is a strong selection for correct mate recognition signals that maximize reproductive fitness. Differences in pheromones within a species can result in pre-mating isolation and possibly speciation. Both S. litura and S. littoralis share the same 11 components that make up their pheromones (in different amounts), with Z9,E11–14:Ac acting as the major component. [13]
The circadian rhythm also affects pheromone release. It has been found that higher amounts of pheromones are released during scotophase (dark period) and that lower levels are released during photophase (light period). This pattern is thought to coincide with male flight patterns, which would maximize responsiveness to the pheromone signals being sent.[14]
There is an inverse relationship between pheromone concentration within the bodies of females and the calling behavior of a female. This most likely relates to the release of pheromones during female calling. It has been previously stated that the accessory gland of a male suppresses female calling and subsequently, re-mating. With calling suppressed, pheromone concentration builds up in the body of mated females. Therefore, when pheromone glands are analyzed, mated females will have a higher titre than virgin females. It is important to note that this result is different from previous studies on other insect species. [14]
Heterospecific matings
Heterospecific matings can be expected for phylogenetically closely related species with adjacent distribution, as is the case for S. litura and S. littoralis. Overlap in pheromone composition as discussed above also contributes to the lack of total reproductive isolation between the two species. Previous experiments have already shown that mating reduces the lifespan of female S. litura. This lifespan decreases even further when mating a heterospecific S. littoralis male. It has also been shown that females lay significantly more eggs after a conspecific mating rather than after a heterospecific mating. Therefore, there is an evolutionary benefit to recognizing and mating with a mate of the same species.[13]
Predators
So far there are a reported 131 species of natural enemies that prey on S. litura at different points in their life cycle. These include different species of parasites that specifically target either the egg, larval, or pupal stage. There are also 36 species of insects and 12 species of spiders that are known to be natural predators to the moths. The identity of the predators vary depending on the various regions. Additionally, infections from fungi and viruses have been observed. For example, in Karnataka, a granulosis virus was found in dead S. litura larvae. Both eggs and larvae were susceptible, and the mortality rate ranged from 50% to 100% depending on the stage of the larvae. The older larvae were killed more rapidly than the younger larvae.[7] However, the most commonly reported viruses are nuclear polyhedrosis viruses,[7] which are also commonly used as pesticides.[15]
There are many ways the predators can locate its prey. One way is the release of chemical cues from the larvae that can act as a locator for predators looking for prey. The predatory stink bug Eocanthecona furcellata is a predator that uses these types of chemical signals to locate and attain its prey. Its prey locating behavior is activated when exposed to two chemical compounds released by S. litura larvae.[16]
Host plants
Spodoptera litura has over 112 host species[9] belonging to over 40 plant families, making the species highly polyphagous. S. litura cause severe damage to their hosts by their vicarious eating habits as larvae. Some common host plants include, but are not limited to: tobacco, cotton, soybean, beet, cabbage, and chickpeas.[3] When the host plant in a particular area is depleted, big groups of larvae will migrate to find a new food source.[7]
Pest activity
Host plants suffer losses when S. litura take residence. During the larval stage, extensive feeding results in the loss of leaves, sometimes leading to the complete stripping of plant leaves.[17] Some external signs of pest activity that can be seen are large holes on leaves, injured stem bases, and discoloration of leaves.[8] Because S. litura acts as a pest on many different kinds of cultivated crops, its presence can cause economic losses in regions where these crops are cultivated. For example, S. litura has been responsible for the 71% yield loss of groundnut in the southern states of India.[3] Another figure shows that S. litura can decrease tobacco yield by 23-50%. This can cause major economic strain since 36 million people are directly or indirectly involved in the production, sale, marketing, or transport of the tobacco crop.[17]The significant impact on agriculture S. litura can have as pests has earned the species a spot on the quarantine list for the United States of America.[8]
Pesticides
Due to its presence in many important crops in agriculture, pesticides are always being applied on the species throughout the year. This has caused the rapid evolution of pesticide and insecticide resistance in S. litura.[9] In addition, the vast amount of pesticides being used have caused concern for pesticide residue on food, environmental damage, and the destruction of beneficial species. Therefore, recent research studies have focused on other biological ways to effectively control these pests.[4]
External Links
- ^ a b c d Yu, Jin-Feng; Li, Cong; Xu, Jin; Liu, Jian-Hong; Ye, Hui. "Male Accessory Gland Secretions Modulate Female Post-Mating Behavior in the Moth Spodoptera litura". Journal of Insect Behavior. 27 (1): 105–116. doi:10.1007/s10905-013-9414-4.
- ^ a b c d "Spodoptera litturalis and Spodoptera litura" (PDF). EPPO. Retrieved October 1, 2017.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ a b c Abbas, Naeem; Shad, Sarfraz Ali; Razaq, Muhammad (2012-07-01). "Fitness cost, cross resistance and realized heritability of resistance to imidacloprid in Spodoptera litura (Lepidoptera: Noctuidae)". Pesticide Biochemistry and Physiology. 103 (3): 181–188. doi:10.1016/j.pestbp.2012.05.001.
- ^ a b Seth, Rakesh K.; Khan, Zubeda; Rao, Dev K.; Zarin, Mahtab (2016-06-01). "Flight Activity and Mating Behavior of Irradiated Spodoptera litura (Lepidoptera: Noctuidae) Males and Their F1 Progeny for Use of Inherited Sterility in Pest Management Approaches". Florida Entomologist. 99 (sp1): 119–130. doi:10.1653/024.099.sp115. ISSN 0015-4040.
- ^ a b c "PM 7/124 (1) Spodoptera littoralis, Spodoptera litura, Spodoptera frugiperda, Spodoptera eridania". EPPO Bulletin. 45 (3): 410–444. 2015-12-01. doi:10.1111/epp.12258. ISSN 1365-2338.
- ^ Lee, Kwang Pum (2010-11-01). "Sex-specific differences in nutrient regulation in a capital breeding caterpillar, Spodoptera litura (Fabricius)". Journal of Insect Physiology. 56 (11): 1685–1695. doi:10.1016/j.jinsphys.2010.06.014.
- ^ a b c d e f g h i j k l m "Spodoptera litura (taro caterpillar)". www.cabi.org. Retrieved 2017-09-26.
- ^ a b c "NOCTUIDAE - Spodoptera litura (Fabricius)" (PDF). LepIntercept. Retrieved October 1, 2017.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ a b c Ahmad, Munir; Saleem, Mushtaq Ahmed; Sayyed, Ali H (2009-03-01). "Efficacy of insecticide mixtures against pyrethroid- and organophosphate-resistant populations of Spodoptera litura (Lepidoptera: Noctuidae)". Pest Management Science. 65 (3): 266–274. doi:10.1002/ps.1681. ISSN 1526-4998.
- ^ Jitendra, Yadav,; Ching-Wen, Tan,; Shaw-Yhi, Hwang, (2010-12-01). "Spatial Variation in Foliar Chemicals Within Radish (Raphanus sativus) Plants and Their Effects on Performance of Spodoptera litura". Environmental Entomology. 39 (6). doi:10.1603/EN10118. ISSN 0046-225X.
{{cite journal}}: CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link) - ^ a b Etman, Ahmed a. M.; Hooper, G. H. S. (1980-04-01). "Developmental and Reproductive Biology of Spodoptera Litura (f.) (lepidoptera: Noctuidae)". Australian Journal of Entomology. 18 (4): 363–372. doi:10.1111/j.1440-6055.1979.tb00868.x. ISSN 1440-6055.
- ^ Fukuda, T.; Wakamura, S.; Arakaki, N.; Yamagishi, K. (April 2004). "Parasitism, development and adult longevity of the egg parasitoid Telenomus nawai (Hymenoptera: Scelionidae) on the eggs of Spodoptera litura (Lepidoptera: Noctuidae)". Bulletin of Entomological Research. 97 (2): 185–190. doi:10.1017/S0007485307004841. ISSN 1475-2670.
- ^ a b c Saveer, Ahmed M.; Becher, Paul G.; Birgersson, Göran; Hansson, Bill S.; Witzgall, Peter; Bengtsson, Marie (2014). "Mate recognition and reproductive isolation in the sibling species Spodoptera littoralis and Spodoptera litura". Frontiers in Ecology and Evolution. 2. doi:10.3389/fevo.2014.00018. ISSN 2296-701X.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ a b c Lu, Qin; Huang, Ling-Yan; Liu, Fang-Tao; Wang, Xia-Fei; Chen, Peng; Xu, Jin; Deng, Jian-Yu; Ye, Hui (2017-06-01). "Sex pheromone titre in the glands of Spodoptera litura females: circadian rhythm and the effects of age and mating". Physiological Entomology. 42 (2): 156–162. doi:10.1111/phen.12185. ISSN 1365-3032.
- ^ "Nuclear Polyhedrosis Virus". Wikipedia. 2017-09-02.
- ^ Yasuda, Tetsuya (1997-03-01). "Chemical cues from Spodoptera litura larvae elicit prey-locating behavior by the predatory stink bug, Eocanthecona furcellata". Entomologia Experimentalis et Applicata. 82 (3): 349–354. doi:10.1046/j.1570-7458.1997.00149.x. ISSN 1570-7458.
- ^ a b Mehta DM, Patil RA; BL, Jat (2014-01-08). "Studies on Life Fecundity Tables of Spodoptera Litura Fabricius on Tobacco Nicotiana tabacum Linnaeus". Entomology, Ornithology & Herpetology: Current Research. 03 (01). doi:10.4172/2161-0983.1000118. ISSN 2161-0983.
{{cite journal}}: CS1 maint: unflagged free DOI (link)