View source for Harlequin cabbage bug

{{Short description|Species of true bug}}
{{Distinguish|harlequin beetle}}
{{Speciesbox
|image = Harlequin Bug adult and nymph.jpg
|image_caption = Adult (left) and nymph (right)
|genus = Murgantia
|species = histrionica
|authority = ([[Carl Wilhelm Hahn|Hahn]], 1834)
}}
[[File:Harlequin cabbage bug (Murgantia histrionica) nymphs.jpg|thumb|Aggregated nymphs]]
The '''harlequin cabbage bug''' ('''''Murgantia histrionica'''''), also known as '''calico bug''', '''fire bug''' or '''harlequin bug''', is a black stinkbug of the family [[Pentatomidae]], brilliantly marked with red, orange, yellow and white markings. It is a major pest of cabbage and related crops in the [[Brassicaceae]], as well as the ornamental flower [[cleome]] throughout tropical and North America, especially the warmer parts of the United States. [[Nymph (biology)|Nymphs]] are active during the summer and in the tropics the bug can achieve three to six generations a year. In the northern range there is only [[Voltinism|one generation annually]] and the insects [[overwinter]] as adults in crop residues or field edges. Organic control involves hand-picking the insects off the plants (they can be dropped into soapy water to drown them) and being especially careful to remove and destroy all the eggs, which are black-and-white striped, laid in clutches of twelve.
==Feeding and chemical defense==
[[File:Harlequin bugs on turnips.jpg|thumb|Young insects slowly destroying a [[turnip]] crop]] Harlequin bugs are [[Herbivore|phytophagous]] insects. Adults and nymphs feed on the stems and leaves of plants such as cabbage, broccoli, kale, turnip, radish, horseradish, mustard and [[rapeseed]], and often cause blotching by their piercing-sucking feeding.<ref name="Aliabadi">{{cite journal|author=Aliabadi, A., Renwick, J.A.A., & Whitman, D.W. |title= Sequestration of glucosinolates by harlequin bug ''Murgantia histrionica''|journal= Journal of Chemical Ecology|volume= 28|issue= 9|pages= 1749–62|pmid=12449503|doi=10.1023/A:1020505016637|year= 2002|s2cid= 36781975}}</ref> These plants are economically important and are abundant in crop fields but when they are not in production, harlequin bugs are able to feed on wild plants as well.<ref name="Ludwig" />
[[Cruciferous vegetables|Cruciferous plants]] such as cabbage produce mustard oil [[glycoside]]s which give them a stinging flavor.<ref name="Aliabadi" /> This chemical compound is sequestered by harlequin bugs and stored in the [[prothorax]] as they feed.<ref name="Aliabadi" /> The adult bugs have been shown to be unpalatable to some species of birds thanks to this chemical defense,<ref name="Aliabadi" /> which could explain their [[aposematism|warning coloration]]. As glucosinolates are often used by crucifers to reduce insect herbivory, their sequestration could also reduce attack rates by insect predators.
== Circulation ==
Like all insects, harlequin bugs have an [[open circulatory system]].<ref name="Craig">{{cite journal|author=Craig, R., & Olson, N.A. |title= Rate of circulation of the body fluid in adult ''Tenebrio molitor'' Linnaeus, ''Anasa tristis'' (Degeer), and ''Murgantia histrionica'' (Hahn)|journal= Science|volume= 113|issue= 2945|pages= 648–50|doi=10.1126/science.113.2945.648 |pmid= 14845697|year= 1951|bibcode= 1951Sci...113..648C}}</ref> Blood is pumped to the head (anteriorly) through the dorsal blood vessel and posteriorly through the ventral [[circulatory system|body cavity]]. To map out the circulation of blood in these insects, Craig et al. injected radioactive phosphorus into the posterior end of the heart and traced it through the body cavity.<ref name="Craig" /> The blood reached the wings first, then the [[antenna (biology)|antennae]], and then pairs of legs in order from anterior to posterior. Craig et al. also tested the time it takes for blood to form a homogeneous mixture (complete mixing). The time it took for blood to completely mix in harlequin bugs was about twenty-five minutes.<ref name="Craig" />
==Mating==
[[File:Harlequin Bug - Murgantia histrionica, near Big Oak Flat, California.jpg|thumb|Mating pair]]
Harlequin bugs reproduce rapidly and females mate multiple times with many males before laying up to 149 eggs per female.<ref name="Ludwig">{{cite journal|author=Ludwig, S.W., & Kok, L.T. |title=Harlequin bug, ''Murgantia histrionica'' (Hahn) (Heteroptera: Pentatomidae) development on three crucifers and feeding damage on broccoli|journal=Crop Protection|volume=20|issue=3|pages=247–251|doi=10.1016/S0261-2194(00)00150-2|year=2001|bibcode=2001CrPro..20..247L }}</ref>
Mating in harlequin bugs is similar to other insects in that the male transfers sperm to the female and the female stores this sperm in a specialized structure called the [[spermatheca]].<ref name="Stacconi">{{cite journal|author=Stacconi, M.R., & Romani, R. |year=2011|title= Ultrastructural and functional aspects of the spermatheca in the American harlequin bug, ''Murgantia histrionica'' (Hemiptera: Pentatomidae)|journal=Neotropical Entomology|volume=40|issue=2|pages=222–30|pmid=21584404|doi=10.1590/S1519-566X2011000200011|doi-access=free}}</ref> Using electron microscopy, Stacconi ''et al''. were able to study the structure of the spermatheca in detail (2011).<ref name="Stacconi"/>
A saccular dilation{{clarify|date=December 2016}} in the [[spermatheca]] stores [[Spermatozoon|spermatozoa]] received from males during copulation.<ref name="Stacconi"/> It can maximize efficiency and use of sperm.<ref name="Stacconi"/> Derived from the [[ectoderm]], the spermatheca is covered in fat and tissue and has three main regions: the distal region, the medial region and the proximal region.<ref name="Stacconi"/> The coiled distal region is responsible for the control of sperm flow. It can modulate how much sperm is excreted which ensures that the female does not lose an excess of sperm.<ref name="Stacconi"/> The proximal region contains valves which prevent the backflow of sperm when muscles dilate. This region is connected to the spermathecal duct where sperm exits.<ref name="Stacconi"/> Stacconi and Romani (2011) found that, overall, the saccular structure within the spermatheca plays a key role in identifying mated and unmated females.<ref name="Stacconi" /> Males are able to identify a mated versus unmated female by the volume of the saccular gland. The study also shows that [[parasitoid]] insects are able to identify mated and unmated females.<ref name="Stacconi"/>
Female [[mate choice]] is based heavily on host plants because male size and coloration, which is important in mating, is determined by the type of host plant they were reared on.<ref name="Hemley">{{cite journal|author=Helmey-Hartman, W.L., & Miller, C.W.|title=Context-dependent mating success in ''Murgantia histrionica'' (Hemiptera: Pentatomidae)|journal=Annals of the Entomological Society of America|volume=107|pages=264–273|doi=10.1603/AN13074|year=2014| s2cid=54089824 |doi-access=free}}</ref> During mating, females also prefer males which have similar odor cues to the host plant of the female.<ref name="Hemley" /> Females of ''M. histrionica'' oviposit on specific plants that are able to provide better nutrition and habitat for their offspring.<ref name="Hemley" /> One study done by Hemley-Hartman and Miller (2014) studied the effects of host plants on female [[Oviparity|oviposition]] site choice.<ref name="Hemley" /> The researchers used broccoli and mustard as two different host plants and found that individuals reared on broccoli were more likely to mate in general and all individuals reared on mustard mated. Individuals reared on mustard were larger than individuals reared on broccoli. Also, the distinctive orange color of ''M. histrionica'' which plays a role in mate choice, was not affected by host plants. This study shows that ''M. histrionica'' have variation in mate choice depending on changing seasons because the availability of these commercial plants also changes with season.<ref name="Hemley" />
== Migration ==
It is important for ''M. histrionica'' to migrate from plant to plant depending on seasonal and insect density changes.<ref name="Englishloeb">{{cite journal|author=Englishloeb, G.M., & Collier, B.D. |title=Nonmigratory movement of adult harlequin bugs ''Murgantia histrionica'' (Hemiptera, Pentatomidae) as affected by sex, age and host plant-quality|journal=American Midland Naturalist|volume=118|issue=1|pages= 189–197|jstor=2425642|doi=10.2307/2425642|year=1987}}</ref> In a study conducted by Englishloeb and Collier (1987), insects released from the original bush had different migration preferences depending on their sex. Males tended to migrate to short distances from the original plant and females mostly remained on the original plant.<ref name="Englishloeb" /> The results of this study were appropriate because males are more inclined to find mates and reduce competition by migrating away from a dense area while females need to oviposit.<ref name="Englishloeb" /> Plants with higher flowering capability were more likely to house females for a long period of time because flowers and buds are able to provide more nourishment for nymphs.<ref name="Englishloeb" />
==Pheromones and aggregation==
''M. histrionica'' males contain 10,11-epoxy-1-bisabolen-3-ol, a [[pheromone]] more commonly known as murgantinol.<ref name="Khrimian">{{cite journal|author=Khrimian, A., Shirali, S., Vermillion, K.E., Siegler, M.A., Guzman, F., Chauhan, K., Aldrich, J.R., & Weber, D.C. |title=Determination of the stereochemistry of the aggregation pheromone of harlequin bug, ''Murgantia histrionica''|journal=Journal of Chemical Ecology|volume=40|issue=11–12|pages=1260–8|pmid=25408429|doi=10.1007/s10886-014-0521-2 |url=https://www.researchgate.net/publication/268795916|year=2014|bibcode=2014JCEco..40.1260K | s2cid=15093682 }}</ref> The [[Stereoisomerism|stereoisomers]] of male harlequin bug pheromones consists of two compounds: [[tridecane]] and murgantinol.<ref name="Khrimian" /> These substances, found specifically in male pheromones, are responsible for aggregation of the insects to aid in sexual reproduction and can also be used in warning predators.<ref name="Zahn">{{cite journal|author=Zahn, D.K., Moreira, J.A., & Millar, J.G. |title=Identification, synthesis, and bioassay of a male-specific aggregation pheromone from the harlequin bug, ''Murgantia histrionica''|journal=Journal of Chemical Ecology|volume=34|issue=2|pages=238–51|doi=10.1007/s10886-007-9415-x|pmid=18204884|year=2008|bibcode=2008JCEco..34..238Z | s2cid=54631212 }}</ref> A study conducted by Zahn ''et al''. (2008) found that mature male insects produced pheromones that recruited females, other males and young insects based on attractiveness. For females, the pheromone is used as a sex-pheromone to attract mates. Other males use a different version of this pheromone to aggregate more males to a given area to signal the availability of food and it serves a similar purpose with nymphs.<ref name="Weber">{{cite journal|author=Weber, D.C., Walsh, G.C., DiMeglio, A.S., Athanas, M.M., Leskey, T.C., & Khrimian, A. |title=Attractiveness of harlequin bug, ''Murgantia histrionica'', aggregation pheromone: field response to isomers, ratios, and dose|journal=Journal of Chemical Ecology|volume=40|issue=11–12|pages=1251–9|doi=10.1007/s10886-014-0519-9|pmid=25380993|url=https://www.researchgate.net/publication/268039395|year=2014|bibcode=2014JCEco..40.1251W | s2cid=6494862 }}</ref> Nymphs use the pheromone to guide themselves to the food source in starving conditions.<ref name="Weber" />
Pheromones can also be used to bait plants that are staples for ''M. histrionica'' and trap the insects. ''M. histrionica'' are major pests of plants in the family [[Brassicaceae]].<ref name="Walsh">{{cite journal|author=Walsh, G.C., Dimeglio, A.S., Khrimian, A., & Weber, D.C.|title=Marking and retention of harlequin bug, ''Murgantia histrionica'' (Hahn) (Hemiptera: Pentatomidae), on pheromone-baited and unbaited plants|journal=Journal of Pest Science|volume=89|pages=21–29|doi=10.1007/s10340-015-0663-1|url=https://www.researchgate.net/publication/275155221|year=2015| s2cid=18870579 }}</ref> In a study conducted by Ludwig and Kok (2001), researchers tested broccoli, mustard and rape plants for attractiveness to the harlequin bug and found that these plants do not significantly delay development in the bugs. This is what leads to these economically important plants to be targeted by ''M. histrionica''.<ref name="Ludwig"/> The study showed that all plants, especially small and young plants even at lower densities of insects, experienced death after being targeted by harlequin bugs, although larger plants could bear more numbers.<ref name="Ludwig"/>
==See also==
* ''[[Dindymus versicolor]]'', an Australian insect also known as the "harlequin bug"
==References==
{{Reflist}}
==External links==
{{Commons category|Murgantia histrionica}}
*{{cite web|url=http://encarta.msn.com/encyclopedia_762507925/cabbage_bug.html|title=Cabbage Bug|archive-url=https://web.archive.org/web/20091102002339/http://encarta.msn.com/encyclopedia_762507925/Cabbage_Bug.html|archive-date=2 November 2009|url-status=dead|publisher=MSN Encarta, Online Encyclopedia, Dictionary, Atlas, and Homework|access-date=24 September 2008}}
*[http://entomology.ifas.ufl.edu/creatures/veg/leaf/harlequin_bug.htm harlequin bug – ''Murgantia histrionica'' (Hahn).] IFAS – Institute of Food and Agricultural Sciences, University of Florida.
*[https://www.britannica.com/animal/harlequin-cabbage-bug Harlequin cabbage bug] - Britannica, T. Editors of Encyclopaedia (2018, October 15). [[Encyclopædia Britannica|Encyclopedia Britannica]].
{{Taxonbar|from=Q765506}}
[[Category:Pentatomini]]
[[Category:Hemiptera of North America]]
[[Category:Insects described in 1834]]
[[Category:Taxa named by Carl Wilhelm Hahn]]
[[Category:Agricultural pest insects]]
[[Category:Invasive agricultural pests]]