Y

Y-Chromosome outbreaks in many port cities in the Americas that involved thousands of human cases. The specter of A sex chromosome that is characteristic of males yellow fever was much feared throughout Africa and in species in which the male typically has two the Americas due to the havoc caused by the disease ­dissimilar sex chromosomes (XY). and the accompanying economic disruption. The last major yellow fever epidemic in the United States occurred in New Orleans in 1905. There were about Yellow Dog Tick, Haemaphysalis 4,000 human cases of yellow fever and nearly 500 leachi (Audouin) (Acari: Ixodidae) people died from yellow fever during this epidemic. The history of yellow fever epidemics pro- This is a common pest of dogs in Africa and Asia. vides numerous examples why this disease inspired  Ticks dread and fear in Africa, the U.S., Central America, the Caribbean and South America. Examples of the numbers of deaths during outbreaks are star- Yellow-Faced Bees tling: 6,000 dead in Barbados in 1647; 3,500 deaths in Philadelphia; 1,500 in New York City in 1798; Members of the family Colletidae (order 29,000 deaths in Haiti in 1802; 20,000 deaths in Hymenoptera, superfamily Apoidae). over 100 American towns in 1878. Yellow fever has  Bees re-emerged with an upsurge of human cases in the  Wasps, Ants, Bees, and Sawflies latter half of the twentieth century. There were 100,000 cases and 30,000 deaths in Ethiopia in 1960–1962; 17,500 cases with 1,700 deaths in Yellow Fever Upper Volta in 1983; Cameroon 20,000 cases with 1,000 deaths in 1990. The World Health Organiza- Walter J. Tabachnick tion officially reported 18,735 yellow fever cases University of Florida, Vero Beach, FL, USA with 4,522 deaths for the period 1987–1991.

The mosquito borne yellow fever virus causes severe disease in humans. Yellow fever was first described Insect Vectors as a disease in the early part of the seventeenth cen- tury. The disease was one of the most devastating Several different mosquito species can be involved and important diseases in Africa and the Americas with the transmission of yellow fever depending during the next 300 years. There were yellow fever on the geographic region and habitat. The most 4298 Y Yellow Fever important mosquito species involved worldwide The Virus in the transmission of yellow fever to humans is Aedes aegypti, also known as “the yellow fever Yellow fever virus is a member of the group of mosquito.” The association between yellow fever viruses called Flavivirus. The virus has been found transmission to humans by Aedes aegypti was a in the tropical regions of the Americas and Africa, major breakthrough in understanding this dread and there have been historical yellow fever incur- disease. Major Walter Reed, U.S. Army, was the sions for brief outbreaks in parts of Europe. The yel- leader of the ­scientists who were able to show the low fever virus has never been demonstrated in role of Aedes aegypti in their work while sta- Asia, Australia or the Pacific despite the presence of tioned in Cuba in 1901. The subspecies Aedes Aedes aegypti in these regions. The reason for this is aegypti aegypti is widely distributed throughout unknown and the subject of much speculation. the tropics and subtropics of the world. This form Although Walter Reed showed Aedes aegypti trans- is able to breed in a variety of artificial containers, mits the agent of yellow fever in 1901, and that the i.e., flower pots, tires, water jars, many commonly agent was smaller than bacteria, it was not until found around human habitats. Aedes aegypti 1927 that yellow fever was shown to be a virus. aegypti also has a distinct preference for humans as a source of blood that makes this species par- ticularly efficient in circulating a pathogen from infected humans to uninfected humans. As a result, The Disease this highly urbanized mosquito species has the capability of sustaining the urban epidemics of Yellow fever symptoms may range from clinically yellow fever that have occurred during the last 300 inapparent to fatal. Studies have shown that in years. The control ofAedes aegypti aegypti popula- some regions of Latin America as much as 90% of tions is considered of primary importance in the population have been infected with yellow reducing the risk of urban areas to yellow fever. fever virus and have no clinical symptoms of There are other mosquitoes that can be ­disease. Once an infected mosquito bites a human, involved in yellow fever virus transmission. In the incubation period is generally 3–6 days. Mild tropical regions of the Western Hemisphere, cases appear similar to many other common mosquitoes in the genus Hemagogus transmit ­illnesses that produce a fever. However, when clin- yellow fever virus to monkeys in the forest can- ical disease occurs, the onset of the disease is very opy. This is called the jungle yellow fever cycle in sudden. There is high fever (102°–104°F), head- the Americas. The danger occurs when these ache, malaise, back pain, chills, prostration, nau- canopy mosquitoes infect humans when trees sea, slow pulse and vomiting. Yellow fever virus are felled for clearing, and the infected human can be found in the blood of the patient for about returns to an urban environment where Aedes 4 days after infection, and as a result the patient aegypti aegypti can become infected, resulting in is capable of infecting mosquitoes during this an urban epidemic. In tropical Africa, the mos- time. Some individuals show a rapid recovery at quito Aedes africanus transmits yellow fever this point and the symptoms stop. This phase can virus between forest dwelling canopy monkeys; last from 3 to 4 days. More severe cases also have Aedes bromeliae, Aedes vittatus and Aedes their symptoms subside for a brief remission but f­ u r c i f e r - t­ a y l o r i transmit the virus to monkeys in symptoms return in a day or so with fever, vomiting, the savanna and gallery forest regions of Central abdominal pain, prostration, dehydration, jaun- Africa. The epidemic danger to humans is when dice due to liver involvement, internal bleeding, infected humans bring the virus to urban centers bleeding of the nose, mouth, gums or in their inhabited by Aedes aegypti. urine, kidney or liver failure. The internal bleeding Yellow Fever Y 4299 results in blood in the vomit, called “black vomit” Aedes aegypti is also cause for concern since Asian due to the color, and dark stools. No virus is in the populations would be extremely susceptible due to blood at this point so the patient is not infectious lack of any native immunity to the yellow fever to mosquitoes. There is no cure; treatment is sup- virus. Asian populations may be extremely vulner- portive to try to reduce the severity of these symp- able to yellow fever with potentially catastrophic toms. This is the diphasic part of yellow fever. consequences. Twenty to fifty percent of people who enter the The ability to interrupt a yellow fever out- second phase die from yellow fever. Death usually break will depend on being able to bring to bear a occurs between the 7th and 10th day of the illness. diverse array of tools including an efficient and Some very severe atypical cases of yellow fever effective­mosquito control program and a massive may die as early as 3 days after the onset of symp- vaccination program. Both are extremely difficult toms. Mortality from yellow fever is about 10% of to accomplish in many regions of the world where clinical cases but has reached as high as 50% of the risk of a ­yellow fever outbreak may be greatest. those people developing symptoms. ­Successful mosquito control against Aedes aegypti Dr. Max Theiler developed a vaccine against has reduced the number of yellow fever cases in yellow fever, called the 17D vaccine, in the 1930s. many cities. However, mosquito control resources In 1951, Dr. Theiler received a Nobel Prize for his may be non-existent and delivery of vaccine work. This vaccine is still widely used and provides ­insufficient. In the 1990s, the worldwide annual excellent protection against yellow fever for 10 production of yellow fever vaccine was about 15 years post-vaccination. There are studies showing million doses with demands on vaccine extremely that protection may be as long lived as 30–35 years unpredictable. A vaccination program that is after being vaccinated in some people. geared to regions in advance of an expected Monkeys also can be infected with yellow ­epidemic is cost effective, but it is unlikely to be fever virus. In most tropical regions of the world ­successful because of the time delay in identifying monkeys serve as the wild host, maintaining the the epidemic and because it takes 5–7 days for the virus in the absence of human involvement. ­vaccine to ­provide any protection after inocula- Many monkey species experience yellow fever tion. On the other hand, a campaign to vaccinate disease and suffer deaths. One of the early signs the entire population in the absence of yellow of yellow fever in a region may be the discovery fever would be extremely costly and require a of dead monkeys. long-term commitment to vaccinate anyone enter- ing the population through birth or immigration. The challenges of yellow fever remain formidable. Impact and Problems  Mosquitoes  History and Insects Yellow fever remains a serious and dread disease in many parts of the world despite advances in understanding mosquito transmission, advances References in mosquito control, advances in understanding human risk and the development of a very effec- Monath TP (1989) Yellow fever. In: Monath TP (ed), The arbo- tive and safe vaccine. The continued appearance of viruses: epidemiology and ecology. CRC Press, Boca ­yellow fever epidemics in Africa, and the appear- Raton, FL, pp 139–231 ance of yellow fever cases in the Americas are all Strode GK (ed) (1951) Yellow fever. McGraw-Hill, New York, NY, 710 pp cause for concern that this dread disease remains Tabachnick WJ (1991) Evolutionary genetics and insect borne very dangerous. In addition, the historical absence disease. The yellow fever mosquito, Aedes aegypti. Am of yellow fever in Asia despite the presence of Entomol 37:14–24 4300 Y Yellow Flies Yellow Flies Life History

Some members of the family Tabanidae (order Generally there are three or four generations Diptera). annually, with broods of adults present in March-  Flies May, May-June, July-August, and August-November.  Horse Flies and Deer Flies (Diptera: Some of the latter brood overwinter as pupae Tabanidae) rather than emerging as adults. Although eggs, lar- vae and adults of yellowstriped armyworm may be present in autumn or early winter, they cannot Yellow Jackets withstand cold weather, and perish. Development time, from egg to adult, is about 40 days. Members of the family Vespidae (order The eggs are greenish to pinkish brown in Hymenoptera). color and bear 45–58 small ridges. In shape, the  Wasps, Ants, Bees, and Sawflies egg is a slightly flattened sphere, measuring 0.46–0.52 mm in diameter and 0.38–0.40 mm in height. Females typically deposit clusters of 200– Yellow Mealworms 500 eggs, usually on the underside of leaves. Total fecundity was determined to be over 3,000 eggs under laboratory conditions. The eggs are  Stored Grain and Flour Insects covered with scales from the body of the adults. Duration of the egg stage is 3–5 days at warm temperatures (Fig. 1). Yellows Larvae initially are gregarious in behavior, but as they mature they disperse, sometimes Some members of the family Pieridae (order spinning strands of silk upon which they are Lepidoptera). blown by the wind. There usually are 6 instars,  Yellow-White Butterflies although 7 instars have been reported. Head cap-  Butterflies and Moths sule widths are about 0.28, 0.45, 0.8–1.0, 1.4–1.6, 2.0–2.2, and 2.8–3.0 mm, respectively, for instars 1–6. The larva grows from about 2.0 to 35 mm in Yellowstriped Armyworm, Spodoptera ornithogalli (Guenée) (Lepidoptera: Noctuidae)

John L. Capinera University of Florida, Gainesville, FL, USA

The distribution of this insect includes most of North America, Central and South America, and many Caribbean islands. As a pest, however, its occurrence is limited principally to the south- eastern USA. A very similar species called west- Yellowstriped Armyworm, Spodoptera ­ornithogalli ern yellowstriped armyworm, Spodoptera praefica (Guenée) (Lepidoptera: ­Noctuidae), Figure 1 Adult (Grote), largely replaces S. ornithogalli in the yellowstriped armyworm, Spodoptera ornithogalli western USA. (Guenée). Yellowstriped Armyworm, Spodoptera ornithogalli (Guenée) (Lepidoptera: Noctuidae) Y 4301 length over the course of development. Duration of the larval stage is 14–20 days, with the first three instars requiring about 2 days each and the last three instars requiring about 3 days each. Coloration is variable, but mature larvae tend to bear a broad brownish band dorsally, with a faint white line at the center. More pronounced are black triangular markings along each side, with a distinct yellow or white line below. A dark line runs laterally through the area of the spiracles, and below this is a pink or orange band. Dark subdorsal spots are found on the mesothorax of yellowstriped armyworm, and the triangular shape of these spots aids in distinguishing this insect from sweetpotato armyworm, Spodoptera dolichos, and velvet armyworm, S. latifascia, in southeastern USA. The head is brown but has extensive blackish markings (Fig. 2). Larvae pupate in the soil within a cell con- taining a thin lining of silk. The reddish brown pupa measures about 18 mm in length. Duration of the pupal stage is 9–22 days, normally averaging 12–18 days. The moths measure 34–41 mm in wing span. The forewings are brownish gray with a compli- Yellowstriped Armyworm, Spodoptera ­ornithogalli cated pattern of light and dark markings. Irregular (Guenée) (Lepidoptera: Noctuidae), Figure 2 whitish bands normally occur diagonally near the Mature larva of yellowstriped armyworm, center of the wings, with additional white color- Spodoptera ornithogalli (Guenée). ation distally near the margin. The hind wings of yellowstriped armyworm are opalescent white, morningglory, Ipomoea sp.; plantain, Plantago with a narrow brown margin; the sexes are dimor- lanceolata; prickly lettuce, Lactuca scariola; and phic. Under laboratory conditions average longev- redroot pigweed, Amaranthus retroflexus. ity of adults is 17 days, with most egg production Several wasp parasitoids affectS. ornithogalli completed by the tenth day. including Rogas laphygmae Viereck, R. terminalis These species are very general feeders, report- (Cresson), Zele mellea (Cresson), Chelonus insu- edly damaging many crops, including alfalfa, laris Cresson and Apanteles griffini Viereck (all blackberry, cotton, clover, grape, lentil, peach, Hymenoptera: Braconidae). Also, Euplectrus plat- rape, raspberry, sorghum, soybean, sugarbeet, hypenae Howard (Hymenoptera: Eulophidae) sweetclover, sunflower, tobacco, wheat, and sev- attacks larvae and causes a cessation of feeding eral vegetable and flower crops. Some of the weed within 2 days. Thus, this parasitoid is particularly species known to be suitable hosts are castorbean, valuable at minimizing damage. Numerous flies Ricinus communis; dock, Rumex sp.; gumweed, have been found to parasitize these armyworms Grindelia sp.; horse nettle, Solanum carolinense; including Archytas spp., Choeteprosopa hede- horseweed, Erigeron canadensis; jimsonweed, manni Brauer and Bergenstamm, Euphorocera Datura sp.; lambsquarters, Chenopodium album; omissa (Reinhard), E. tachinomoides Townsend, 4302 Y Yellow-White Butterflies (Lepidoptera: Pieridae) Lespesia aletiae (Riley), L. archippivora (Riley), ­ornithogalli. Entomologia Experimentalis et Appli- Omotoma fumiferanae (Tothill), Winthemia cata 58:159–164 Capinera JL (2001) Handbook of vegetable pests. Academic quadripustulata (Fabricius), and W. rufopicta Press, San Diego, 729 pp (Bigot) (all Diptera: Tachinidae). A nuclear poly- Crumb SE (1929) Tobacco cutworms. USDA Tech Bull 88, hedrosis virus is highly pathogenic to larvae, and 179 pp survivors that do not succumb exhibit reduced Crumb SE (1956) The larvae of the Phalaenidae. USDA Tech Bull 1135, 356 pp fecundity. Undoubtedly predators are important, but their effect has not been quantified. Yellow-White Butterflies Damage (Lepidoptera: Pieridae)

Larvae damage plants principally by consumption John B. Heppner of foliage. The small, gregarious larvae tend to Florida State Collection of Arthropods, Gaines- skeletonize foliage but as the larvae grow and dis- ville, FL, USA perse they consume irregular patches of foliage or entire leaves. However, they will also feed on the Yellow-white butterflies, family Pieridae (includ- fruits of tomato, cotton, and other plants. Larval ing jezebels, orangetips, sulphurs, whites, and consumption of soybean was estimated to total alfalfa and cabbage butterflies), total about 1,275 115 sq cm; this is an intermediate value relative to species worldwide, most being Indo-Australian some other lepidopterous defoliators. (ca. 515 sp.). Four subfamilies are recognized: Pseudopontiinae (a single African species), Dis- morphiinae, Pierinae, and Coliadinae. The fam- Management ily is in the superfamily Papilionoidea (series Papilioniformes), in the section Cossina, sub- Insecticides are applied to foliage to prevent injury section Bombycina, of the division Ditrysia. by larvae. The microbial insecticide Bacillus thur- Adults small to large (23–100 mm wingspan); ingiensis can be applied to kill armyworms, but antennae often with weak clubs. Wings mostly should be applied when the larvae are young as triangular or rounded; hindwings usually small they become difficult to control as they mature. and rounded, but sometimes larger than fore- Larvae will consume bran bait containing wings and somewhat pointed (Dismorphiinae); insecticide. body usually slender but sometimes robust. Proximity of crops to rangeland containing Maculation usually variously yellow or white, weed hosts, or to alfalfa, may be important factors with darker spots or patches of various shape predisposing other crops to injury. At high densi- (rarely without markings); rarely hyaline; some- ties, especially if alfalfa hay is mowed, larvae will times very colorful, and many with special UV sometime disperse simultaneously and invade coloration ve different from what is evident nearby fields. Physical barriers such as trenches under white light. Pierinae are mostly white can be used to deter such dispersal. species and Coliadinae have more of the color- ful and yellow species; many pierid colorations are from pterin or flavone deposits. Adults diur- References nal. Larvae leaf feeding (one species feeds gre- gariously in Mexico). Various plants are utilized, Adler PH, Willey MB, Bowen MR (1991) Temporal including Capparidaceae, Leguminosae, Loran- ­oviposition patterns of Heliothis zea and Spodoptera thaceae, and Santalaceae, among others, but Young, Jr., David A Y 4303 Yolk

The nutritive matter of the egg, from which the developing embryo derives sustenance.  Embryogenesis  Endocrine Regulation of Insect Reproduction  Oogenesis

Yponomeutidae

Yellow-White Butterflies (Lepidoptera: Pieridae), A family of moths (order Lepidoptera). They com- Figure 3 Example of yellow-white butterflies monly are known as ermine moths. (Pieridae), Anthocharis sara Lucas from California,  Ermine Moths USA.  Butterflies and Moths especially Cruciferae. Some economic species are known, particularly on cabbages and other Young, Jr., David A crucifers (Fig. 3). David Young was born May 26, 1915, at Wilkins- burg, Pennsylvania, USA. He obtained a B.A. References degree from the University of Louisville in 1939 and then taught science in the public school sys-

Courtney SP (1986) The ecology of pierid butterflies: dynam- tem from 1939 to 1941. In 1942 he was awarded ics and interactions. Adv Ecol Res 15:51–131 a M.S. from Cornell University. Serving in the Eitschberger U (1984) Systematische Untersuchungen am military during World War II, he returned to Pieris napi-bryoniae-Komplex (s.l.) (Lepidoptera, Pieri- serve as an instructor at the University of Louis- dae). In: Herbipoliana. Marktleuthen. 2 volumes (1104 pp., 101 pl.) ville from 1946 to 1948. He also studied at the Feltwell J (1982) Large white butterfly. The biology, biochemis- University of Kansas, and was awarded a Ph.D. try and physiology of Pieris brassicae (Linnaeus). W Junk, in 1950. Young then joined the United States The Hague. 538 pp (In Series Entomologica, 18) National Museum and was employed by the Krzywicki M (1962) Pieridae. In: Klucze do Oznaczania Owadów Polski. 27. Motyle – Lepidoptera, 65: 1–45, 1 pl. Insect Identification and Foreign Parasite Intro- [part]. Polskie Towardzystwo Entomologiczne [in Pol- duction Section of USDA from 1950 to 1957. ish], Warsaw Young joined the faculty of North Carolina State Pleisch E, Sonderegger P (eds) (1987) Pieridae – Weisslinge. In: Schmetterl inge und ihre Lebensräume: Arten – University in 1957, where he retired in 1980 but Gefährdung – Schutz. Schweiz und angrenzenden Gebi- continued his writing until 1986. Young was an ete, 1: 136–162, pl. 2–4. Pro Natura-Schweizerische internationally acclaimed leafhopper specialist. Bund fuer Naturschutz, Basel He described 807 new species, 207 new genera, Seitz A (ed) (1906–31) Familie: Pieridae. In: Die Gross- Schmetterlinge der Erde, 1: 39–74, pl. 17–27 (1906–07); and a new tribe. Among other publications, he 1(suppl.): 93–125, 332–335, pl. 7 (1930–31); 5:53–111, authored the monumental “Taxonomic study of 1014–1026, pl. 18–30 (1908–24); 9: 119–190, pl. 50–73 the Cicadellinae (Hemiptera: Cicadellidae),” (1909–10); 13:29–69, pl. 10–22 (1910). A Kernen, which was published in three parts and treated Stuttgart Talbot G (1932–1935) Pieridae. In: Lepidopterorum Catalo- 292 genera from throughout the world. He died gus, 53, 60: 1–697. W Junk, Berlin on June 8, 1991. 4304 Y Yucca Moths (Lepidoptera: Prodoxidae) Reference four-segmented). Maculation often is white with various darker markings, or more colorful and iri- Deitz LL (1991) David A. Young, Jr. Am Entomol 37:251 descent. Adults are diurnal. Larvae are seed, flower stalk, or stem borers; rarely gall makers. Host plants are various yucca plants (Agavaceae) for the Yucca Moths (Lepidoptera: well-known yucca pollinators of North America, Prodoxidae) while other species (Lamproniinae) are on hard- wood trees and bushes. John B. Heppner Florida State Collection of Arthropods, Gaines- ville, FL, USA References Yucca moths, family Prodoxidae, total 65 species, Davis DR (1967) A revision of the moths of the subfamily mostly western Nearctic, but now also including Prodoxinae (Lepidoptera: Incurvariidae). Bull U S Natl some genera (Lamproniinae) from other regions Mus 255:1–170 that previously were placed in Incurvariidae. The Nielsen ES, Davis DR (1985) First Southern Hemisphere family is in the superfamily Incurvarioidea, in the prodoxid and the phylogeny of the Incurvarioidea (Lepidoptera). Syst Entomol 10:307–322 section Incurvariina, of division Monotrysia, Pellmyr O (1999) Systematic revision of the yucca moths in infraorder Heteroneura. There are two subfami- the Tegeticula yuccasella complex (Lepidoptera: Pro- lies: Prodoxinae and Lamproniinae. Adults small doxidae) north of Mexico. Syst Entomol 24:243–271 (5–33 mm wingspan), with rough head scaling; Powell JA, Mackie RA (1966) Biological interrelationships of moths and Yucca whipplei (Lepidoptera: Gelechiidae, haustellum reduced, scaled; labial palpi porrect; Blastobasidae, Prodoxidae). Univ Calif Publ Entomol maxillary palpi folded, five-segmented (rarely 42:1–59