Average Number Of Larvae Research Articles

Dispersion of the Mediterranean fruit fly Ceratitis capitata Wiedem. (Diptera: Tephritidae) in mandarin orchards on Montenegrin seacoast

The Mediterranean fruit fly Ceratitis capitata Widem. has been an established pest on the Montenegrin seacoast for more than ten years, although with variable abundance in different years and localities. From an economic aspect, its most important host in Montenegro is the mandarin unshiu (Citrus unshiu Marc.), particularly its cultivar Owari. Dispersion of C. capitata in citrus orchards (prevailingly mandarin) was monitored on Baosici, Lastva Grbaljska and Bar localities during 2003 and 2004. The results of this study showed that, during both years, peripheral-row trees (primarily the first row) in citrus orchards were more exposed to attacks by C. capitata than middle and last rows. In 2003, the average number of larvae in mandarin fruits in first rows varied from 11.4?0.59 to 40.1?0.67, from 7.04?0.47 to 28.8?0.48 and from 2.9?0.07 to 17.3?0.54 on the localities of Baosici, Lastva Grbaljska and Bar, respectively. On the same localities, it ranged from 7.4?0.34 to 16.9?0.4, from 0.0 to 18.7?0.32 and from 0.0 to 9.93?0.56 in middle rows, and from 3.0?0.28 to 16.8?0.77, from 0.0 to 20.9?0.38 and from 0.0 to 13.1?0.39 in last rows. Data collected at Baosici, Lastva Grbaljska and Bar in 2003 also suggest that the average number of larvae per mandarin fruit in first rows was 1.78-2.08 times higher than in middle rows, and 1.25-1.77 times higher than in last rows. In 2004, the average number of larvae in mandarin fruits in first rows varied from 7.3?0.27 to 8.3?0.45, from 7.2?0.23 to 17.6?0.59 and from 3.8?0.1 to 8.8?0.25 on the localities of Baosici, Lastva Grbaljska and Bar, respectively. On these localities, it ranged from 1.7 ?0.17 to 3.3?0.19, from 1.1?0.12 to 3.5?0.8 and from 0.0 to 0.8?0.14 in middle rows, and from 1.7?0.17 to 3.6?0.32, from 0.0 to 4.0?0.26 and from 0.0 to 0.2?0.06 in last rows. Data collected in 2004 also showed that the average number of larvae in mandarin fruits in first rows on the same localities was 3.12-15.75 times higher than in middle rows, and 2.94 -6.3 times higher than in last rows.

북한강 참다슬기, Semisulcospira coreana (v. Martens) 의 번식생태

북한강에 서식하고 있는 참다슬기의 산란생태를 파악하기 위하여 생식소 발달단계에 따른 생식주기, 성비, 군성숙도, 보육낭유생의 월별변화 등 번식생태와 관련된 생물학적 기초 자료를 조사하였다. 각고에 대한 각경, 전중, 육중의 상관계수 (<TEX>$R^2$</TEX>) 는 0.7761-0.8719로 비교적 높은 상관관계를 나타내었다. 참다슬기의 암컷 생식소는 청록색, 수컷 생식소는 옅은 황색을 띠고, 암컷은 유생을 기르는 보육낭 (brood pouch) 을 가지고 있었다. 암수성비는 0.17-0.58의 범위로 계절적 불균형이 심하였으며, 여름철 암컷 비율이 높고 겨울철 암컷비율이 낮았다. 생식소의 조직학적 조사 및 비만지수, 생식소지수 조사 결과 봄, 가을에 두 번의 정점을 나타낸 후 급격히 떨어지는 경향을 보여 생식소 발달은 봄, 가을 연 2회 이루어짐을 알 수 있으며, 암컷 보육낭속의 유생수 월별변화도 연중 두 번의 피크를 나타냈었고, 보육낭속의 유생수는 월 평균 286-975범위로, 11월에 연중 가장 적었고 3월과 9월에 각각 975개, 863개로 연중 가장 많은 유생을 보유하였다. 50%가 성숙하는 군성숙체장은 각고 13.95 mm였으며, 각고 15mm 이상은 모든 개체가 성숙하고 보육낭을 형성하였다. To clarify reproductive ecology of the melania snail Semisulcospira coreana (v. Martens, 1886) in Bukhan River, gonad development, fatness, gonad index, sex ratio, first sexual maturity of population, monthly change of larvae number and developmental stages in brood pouches were investigated by six identification methods. As maturation progrsses, the sex of the snali can be distinguishable easily by color:: the ovary being blue-green and testis light yellow. The sex ratio of female to male individuals over 13.95 mm shell height was significantly different from 1:1 (<TEX>${\chi}^2$</TEX> = 38.45, p < 0.05). The sex ratio of female to male individuals changed drastically according to the season, Based on the monthly variations of fatness, gonad index and histological analysis, spawning occurred twice a year (spring and autumn) and the mean size of matured eggs was <TEX>$450{\mu}m$</TEX> in diameter. The monthly change of larval number in brood pouch showed also two distinct peaks in March and September during the year. The average number of larvae in brood pouches was 286 - 862 individuals. In this study, the number of larvae in the brood pouches were a minimum in December and a maximum in March (975 larvae). The biological minimum size (the size at 50% of group sexual maturity) of the melania snail was 13.95 mm in shell height in females and males. All females over 15 mm in shell height possesed brood pouches.

Variação sazonal de espécies de tripes em videira de acordo com sistemas de manejo e fases fenológicas

O objetivo deste trabalho foi avaliar a ocorrência de espécies de tripes em videira e a flutuação populacional, das espécies mais frequentes e abundantes, em diferentes fases fenológicas e sistemas de manejo. O experimento foi realizado em Petrolina, PE, em cinco parreirais - três da cultivar Sugraone (certificada, semiconvencional e convencional) e duas da cultivar Brasil (certificada e convencional). Foram coletadas folhas e inflorescências durante dois anos consecutivos (2008-2010), em 15 plantas. Foram realizadas análises de correlação entre as médias de infestação de tripes e os fatores meteorológicos temperatura, umidade relativa do ar e precipitação pluvial. O número médio de larvas e adultos de tripes foi comparado entre os sistemas de manejo e as fases fenológicas. Nas folhas, foram constatadas as espécies Heliothrips haemorrhoidalis, Retithrips syriacus, Selenothrips rubrocinctus, Frankliniella schultzei, Frankliniella sp. e Scolothrips sp., além de larvas de Aelothripidae. Nas inflorescências, foram identificadas apenas espécies de Thripidae, F. schultzei, F. brevicaulis, F. rodeos, F. gardeniae e Frankliniella sp. Não houve correlação de temperatura, umidade relativa e precipitação pluvial com o número médio de tripes. Existe um complexo de espécies de tripes na videira, e a fenologia da planta exerce influência na abundância desses insetos.

Effects of dietary non-starch polysaccharides on establishment and fecundity of Heterakis gallinarum in grower layers

It was hypothesized that the establishment and fecundity of Histomonas meleagridis free Heterakis gallinarum may be affected by dietary non-starch polysaccharides (NSPs). One-day-old female layer chicks (N=670) were fed ad libitum for 11wk one of the following diets in a three-times repeated experiment: basal diet (CON), basal diet plus pea bran rich in insoluble NSP (I-NSP), basal diet plus chicory root meal as a source of inulin rich soluble NSP (S-NSP). At the end of wk three, each feeding group was subdivided into an uninfected and an infected group of birds each being inoculated with a placebo or with 200 H. meleagridis free eggs of H. gallinarum. The birds were slaughtered 8wk post infection and their worm burdens, the nematode egg excretion, caeca sizes and weights as well as intracaecal pH and volatile fatty acid (VFA) concentrations were determined.The NSP supplemented diets and also infection led to reduced body weights (BWs) of birds and impaired the feed conversion rate (P<0.001). The NSP supplemented diets increased average length of caecum (P<0.001) with S-NSP exerting a stronger effect than I-NSP (P<0.05). Full caeca weight was increased by S-NSP (P<0.001). Feeding S-NSP lowered intracaecal pH and molar proportion of acetate and increased that of butyrate compared to CON and I-NSP (P<0.001). Caecal pool of VFA was increased with S-NSP (P<0.001).The NSP-diets elevated incidence of infection (P<0.01), average number of larvae (P<0.009) and total worm burden (P<0.001) compared to CON. The daily amount of faeces increased in NSP-fed birds (P<0.001). Number of eggs per gram of faeces (EPG), number of eggs excreted per worm population of a bird within 24h (EPD) and female worm fecundity (EPD/female worm) were elevated after feeding S-NSP (P≤0.002), whereas I-NSP led to lower EPG/female worm (P<0.05). The EPD increased in the sequence of CON<I-NSP<S-NSP (P<0.001).It is concluded that the pea bran and chicory root meal used as sources of insoluble and soluble dietary NSPs, respectively, provided favourable conditions for the establishment of H. gallinarum in grower layers. Chicory root meal additionally enhanced fecundity of the nematode. Therefore, the two natural sources of insoluble and soluble NSPs offer no potential as protecting agents against H. gallinarum infections in chicken.

아까시잎혹파리, Obolodiplosis robiniae (Diptera: Cecidomyiidae) 연간 밀도변동과 아까시나무 수관 내 분포

Locust gall midge (LGM), Obolodiplosis robiniae (Haldeman) (Diptera: Cecidomyiidae), is a cecidomyiid insect forming roll-up galls on leaves of Robinia pseudoacacia Linnaeus (Fabaceae). LGM, known as native to North America, was reported from Korea and Japan in 2002. LGM was observed weekly or biweekly to clarify their voltinism and distribution within the crown of the host tree in two sites of Osan and Siheung in Korea from May to August, 2007. Density of LGM was investigated based on the number of larvae per leaf. Two generations of LGM were observed in Siheung site whereas three generations in Osan site during the present study. The result indicated that LGM had at maximum three generations per year. The density of LGM in Osan was higher in the upper crown of the host trees than middle or lower part. In Siheung, LGMs were distributed more on the exterior of the lower crown than the interior. The average number of larvae per gall was and individuals per leaf in Osan and Siheung, respectively.

SEASONAL FLUCTUATION OF HELICOVERPA ARMIGERA (HUBNER) (LEPIDOPTERA: NOCTUIDAE) ON COTTON AND OKRA AND HEAT UNITS RELATED

The seasonal fluctuation of the American bollworm (ABW), Helicoverpa armigera (Hub.), (moths and larvae) was studied on cotton, Gossypium barbadense and okra, Hibiscus esculentus, in Dakahlia Governorate during 2007 and 2008 cotton seasons. Results revealed that the population of ABW male moths occurring three peaks each season. The first peak had highest average number of male moths than others during the two seasons. Populations of ABW larvae infest cotton and okra plants appeared two peaks during the same period. The average numbers of larvae on okra was higher than cotton during the two seasons and average. The probability regression values revealed highly significant between accumulated heat units and each of ABW male moths and larval infestation in cotton and okra. The calculated R^2 values ranged between 0.8148 and 0.9619. The same trend was found between accumulated ABW male moths and larval infestation in cotton and okra. The calculated R^2 values ranged between 0.9185 and 0.9793. Also, between larval infestation in okra and cotton plants were highly significant. The calculated R^2 values ranged between 0.6030 and 0.9899. Consequently, accumulated heat units can be used to predict pheromone traps catch and larval infestation on okra and cotton. Pheromone traps catch can be used to predict larval infestation on okra and cotton also can be used larval infestation on okra to predict larval infestation on cotton.

EFFECTIVENESS OF ACCUMULATED HEAT UNITS ON POPULATION FLUCTUATION OF SPINY BOLLWORM AND ASSOCIATED PREDATORS IN COTTON AND MAIZE FIELDS

The seasonal fluctuation of the spiny bollworm (SBW), moths, larvae and associated common predators in relation to accumulated heat units, were studied on cotton, Gossypium barbadense, variety Giza 86 and maize, Zea maize (Single cross, 3062), in Gharbia Governorate during two successive seasons, 2007and 2008. Results revealed that the population of male moths occurring five and four peaks for the two cotton seasons, respectively. The larval infestation of SBW on cotton showed up three peaks each successive cotton season. The average number of larvae at the second peak had low average number than the first and third peaks. On the other hand, the larval infestation of SBW on maize occurred in one peak during the appearance of maize flowers male (tassel) and female (silk) and growing ears. The peak of larval infestation on the maize was more than the second peak in the cotton with about five times. Common predators on cotton occurred in three and two peaks during the two seasons, respectively, while on maize, it occurred in two peaks/season. The population of common predators in the maize was lower than in the cotton fields. Regression values between accumulated heat units as independent factor and SBW male moths, larval infestation and common predators in cotton or maize as dependent factors revealed highly significant during the two seasons. The obverse r2 values ranged between 0.4883 and 0.9730. The same trend was found between accumulated SBW male moths and larval infestation in cotton. The obverse r2 values ranged between 0.7078 and 0.9182. Also, the relationships between larval infestations in cotton or maize and associated common predators were highly significant. The obverse r2 values ranged between 0.3875 and 0.9864. General revealed that the accumulated heat units, captured male moths in pheromone traps can be used to predict larval infestation in cotton and maize crops.

Linking environmental warming to the fitness of the invasive clam Corbicula fluminea

AbstractClimate warming is discussed as a factor that can favour the success of invasive species. In the present study, we analysed potential fitness gains of moderate warming (3 °C above field temperature) on the invasive clam Corbicula fluminea during summer and winter. The experiments were conducted under seminatural conditions in a bypass‐system of a large river (Rhine, Germany). We showed that warming in late summer results in a significant decrease in the clams' growth rates (body mass and shell length increase) and an increase in mortality rate. The addition of planktonic food dampens the negative effect of warming on the growth rates. This suggests that the reason for the negative growth effect of temperature increase in late summer is a negative energetic balance caused by an enhanced metabolic rate at limited food levels. Warming during early summer revealed contrasting effects with respect of body mass (no warming effect) and shell length (increased shell growth with warming). This differential control of both parameters further enhances the loss of the relative (size‐specific) body mass with warming. In contrast, warming in winter had a consistently positive effect on the clams' growth rate as demonstrated in two independent experiments. Furthermore, the reproduction success (as measured by the average number of larvae per clam) during the main breeding period (April) was strongly enhanced by experimental warming during winter, i.e. by eight times during the relatively cold winter 2005/2006 and by 2.6 times during the relatively warm winter 2007/2008. This strong, positive effect of moderate winter warming on the clams' fitness is probably one reason for the recent invasion success of C. fluminea in the northern hemisphere. However, warm summer events might counteract the positive winter warming effect, which could balance out the fitness gains.

Short report on the effect of a parasitic isopod on the reproductive performance of a shrimp

The present work studied the degree of inhibition caused by the bopyrid isopod Eophryxus lysmatae ( Caroli, 1930 [Caroli, E., 1930. Notizia di tre specie nuove ed una poco nota di Bopiridi addominali, parassiti di Caridei del golfo di Napoli. (Contributo alla conoscenza del genere Phrixus Rathke). Boll. Soc. Nat. Napoli 41, 258–269]), an abdominal parasite, on the reproductive performance of its host, the protandric simultaneous hermaphrodite shrimp Lysmata seticaudata (Risso, 1816). Parasitized shrimp (PS) was not able to produce embryos, although they could successfully fertilise the eggs of unparasitized shrimp (US). All US paired with PS were able to fertilise eggs when paired with other US. The average number of larvae (±S.D.) produced by US shrimp paired with US and PS (344±27 and 346±23, respectively) was not significantly different ( p=0.73). The average intermolt period duration (±S.D.) for US and PS (10±1.2 and 11±0.8 days, respectively) was not significantly different ( p=0.82), with bopyrid parasites molting synchronously with their host. No PS lost its parasite during ecdysis. Although only three parasitized shrimp were used in the present work, parasitic castration induced by E. lysmatae seems to only affect the female sexual system of the simultaneous hermaphrodite L. seticaudata, and therefore parasite-induced “reproductive death” does not occur in this species as in other gonochoric and sequencial hermaphroditic caridean shrimp. Nutritional drain and disruption of endocrine mechanisms possibly caused by the bopyrid parasite are discussed.

Novel observations of midge and mosquito larval population dynamics in leaves of the northern pitcher plant, Sarracenia purpurea L.

The invertebrate communities in Sarracenia purpurea were characterized by surveying the contents of 474 leaves from six pitcher plant populations in the eastern United States. More than 8200 invertebrate specimens, both living and dead, were recovered. Midge and mosquito larvae comprised 7907 (96%) of the specimens, with a mean of 16.9 dipteran larvae per leaf. Although midge larvae were present at all collection sites, mosquito larvae were absent from two of the sites. In the latter sites, the number of midge larvae per leaf was greater. This report documents for the first time that there is no statistical difference between the average number of Diptera larvae per leaf for sites that contain both midge and mosquito larvae compared to sites that contain only midge larvae. It appears that pitcher plants maintain an average number of larvae per leaf based on a number of interacting factors which we do not fully understand. This investigation documents that in the absence of mosquito larvae, more midge larvae are found per leaf per leaf than would be predicted based on data from sites that contain both larval taxa.

Changes in transmission of Baylisascarisprocyonis to intermediate hosts as a function of spatial scale

Physical changes in landscapes alter the abundance and distribution of species. Higher‐order effects can occur when changes in ecological processes result in altered interspecific interactions and subsequent changes in a species’ abundance or persistence. Baylisascarisprocyonis, a roundworm parasite of raccoons (Procyonlotor), is pathogenic to numerous small vertebrates that serve as intermediate hosts, including white‐footed mice (Peromyscusleucopus). Raccoons have responded positively to agriculturally induced changes in landscapes, with potential consequences for intermediate hosts of B. procyonis. We examined white‐footed mice from a homogeneous, predominantly forested landscape in south‐central Indiana and a heterogeneous, predominantly agricultural landscape in northwestern Indiana for presence of larval B. procyonis. We compared prevalence of infection, intensity of infection, and average number of larvae per mouse between the landscapes, and among forest patches within the highly fragmented agricultural landscape. Prevalence, intensity of infection, and average number of larvae were significantly higher in the highly fragmented landscape. Within the agricultural landscape, regression models predicted probability of infection, intensity of infection, and average number of larvae per mouse per patch as functions of forest patch area and isolation. We conclude that positive responses of raccoons to agriculturally induced fragmentation of forests have resulted in increased encounter rates between white‐footed mice and infective stages of B. procyonis between and within landscapes, resulting in increased transmission of the parasite to intermediate hosts.

BIOLOGY OF CYPHOCLEONVS ACHATES (COLEOPTERA: CURCULIONIDAE), PROPAGATED FOR THE BIOLOGICAL CONTROL OF KNAPWEEDS (ASTERACEAE)

AbstractCyphocleonus achates (Fahraeus) is a weevil used for the biological control of diffuse knapweed, Centaurea diffusa Monnet Del La Marck, and spotted knapweed, Centaurea maculosa Monnet Del La Marck, in North America. This research provided specific information on the biology of this insect in British Columbia. Adult weevils were released at six densities (1, 2, 4, 8, 16, and 32 male–female pairs) in each of 2 years into plots containing spotted knapweed. Larvae per plant, larval mass, larval survival, adult emergence, and air temperature were measured. Larval production increased with the release density of weevils in both the 1992 cohort and the 1993 cohort. Larval mass did not differ between years. Larval mass also did not vary with the release density of adults or the number of larvae per root. Larval survival of the 1993 cohort ranged from 17 to 48%, whereas that of the 1994 cohort ranged from 0 to 91%. Adult emergence began after the accumulation of 726–1144 degree-days. For both cohorts the date of first emergence occurred earlier, as the average number of larvae per plant increased for both cohorts. Increasing competition for food or space in the roots can induce early emergence. Sex ratios did not vary with date of emergence or release density of adult weevils. Adult emergence increased with the release density in the 1992 cohort, suggesting the average larval densities did not exceed the carrying capacity of the roots. The peak emergence rate increased with the release density in the 1992 cohort, but not in the 1993 cohort because of lower larval survival.

Insecticide Rescue Treatments for Control of First-Generation European Corn Borer in South Dakota, 1997

Abstract Corn fields near New Holland and Letcher, South Dakota were used to evaluate planting-time and postemergence insecticides for controlling first-generation European corn borer, Ostrinia nubilalis Hubner, larvae. Preapplication counts (4 d before application) at Letcher indicated a uniform infestation of O. nubilalis larvae in 92.0% of plants sampled. Approximately 2.4 larvae (4.2, 62.5 and 33.3% were 1st, 2nd and 3rd instars, respectively) per plant were observed at this location. Similarly at New Holland a 90% infestation level (predominantly 1st and 2nd instars on the application date) existed, but the average number of larvae was estimated to be ~ 4-fold less than at Letcher). The at-planting-time treatment at New Holland occurred on 15 May and all whorl-treatments (approximately 1 week prior to tasseling) on 12 July (Letcher) and 15 July (New Holland). Insecticides were applied to single-row plots (16.4 cm by 30.5 m) in a randomized complete block design with 4 replicates. Granules were directed into corn plant’s whorl using a pneumatic applicator powered by a 3.5-horsepower engine mounted on a highboy. Noble metering units attached to a modified chain-driven apparatus regulated the amount of granules released into the pneumatic applicator. Liquid treatments were applied to corn plant whorls using a single-nozzle 3-gal. CO2-propelled backpack sprayer system. Approximately one month following insecticide applications (11 August), twenty corn stalks were randomly chosen from each plot. Each plant was split vertically and examined for O. nubilalis tunneling damage. The number and length of O. nubilalis cavities were analyzed using the ANOVA procedure with means being compared with the LSD.

相模湾および駿河湾の魚介類におけるアニサキス幼虫感染

A total of 5, 555 fishes (17 marine fish and 1 squid species) from Sagami and Suruga Bays were examined for Anisakis larvae in 1995 to 1996. The larvae were detected from 6.1% of Japanese anchovies, 33.7% of chub macherels, 2.0% of white-tipped macherel scads and 23.1% of frigate macherels collected from Sagami Bay, as well as from 3.5% of Japanese anchovies, 0.5% of Japanese pilchards, 21.0% of chub macherels and 33.3% of dolphinfishes collected from Suruga Bay. The average numbers of larvae per fish were 1.5 (1 to 3) and 6.5 (1 to 31) in Japanese anchovies and chub mackerels, respectively. Most larvae parasitized in the visceral organs and abdominal cavity, while a few in the muscles. Most larvae obtained were of Anisakis Type I larvae, Anisakis simplex, and a small number of Anisakis Type II and IV, Contracaecum Type B and D and Spirurid larvae were detecfed.

Control of Southern Armyworm Spodoptera Eridania in Staked Tomato, 1995

Abstract Greenhouse raised seedlings of “Neptune” tomato were planted 27 Sep 18 inches apart into twelve fertilized and sub-irrigated beds, 32” wide and 240 ft long. Beds were fumigated with a 67/339 mixture of methyl bromide and chloropicrin at a rate of 220 lb. acre, covered with white-sided polyethylene-mulch, and divided into 10 plots ca 24 ft long and 3 rows wide. A RCB design was used to assign treatments into 4 replications. Kocide 101 and Maneb 80 WP were sprayed weekly with alternating combinations of Maneb 80 WP at 1 lb/acre plus Kocide 101 at 3 lb/acre and Bravo 720 at 1.5 pt/acre for disease control. Six treatment applications were applied weekly with a high-clearance sprayer using a hydraulic pump operating at 200 psi. The sprayer was equipped with 2 drop nozzles per row, each configured with 3 yellow Albuz nozzles on 14 Nov. for a delivery rate of 76 gpa, increasing to 4 nozzles to deliver 103 gpa for the remaining applications Latron CS-7 was tank-mixed at 16 pz/100 gallon spray for all treatments. Foliar damage and larval counts were made weekly from the south side of 18 plants per plot by randomly selecting 3 pairs of plants between the 4 center stakes of each row, moving to the next pair of plants if any in the first six were atypical. Foliar damage was evaluated visually using a Horsfall type rating scale where 1 = no apparent damage, 2 = 0-1% leaf area removed, 3 = 2-5%. 4 = 6-10%, 5 = 11-30%, and 6 = &amp;gt;30% leaf area removed. The numbers of larvae (SAW and an occasional beet armyworm) were recorded by size (small, medium, large) and species per plant. A precount of 160 plants on 13 Nov showed 55% to have an average foliar damage of less than 1% and average number of larvae to be 4 small, 1.4 medium and 0.23 large per plant. Fruit was harvested from 24 plants per plot and marketable fruit was graded on a commercial table with weights and numbers recorded. Unmarketable fruit was counted and weighed. Value of harvest was calculated on a $5, 7, 9, 12 market for small, medium, large and extra-large fruit, respectively.

The problem of optimal clutch size in a tritrophic system: the oviposition strategy of the thistle gallfly Urophora cardui (Diptera, Tephritidae).

The problem of optimal clutch sizes is a central theme in life history theory. Optimal allocation of eggs is especially complicated for insects in tritrophic systems. In this study we analyze some of the processes determining clutch sizes of the thistle gallfly Urophora cardui, a monophagous tephritid fly associated with Cirsium arvense. U. cardui forms multilocular shoot galls, which vary broadly in their size and number of their gall cells. We investigate various fitness consequences of gall size. An analysis of the number of cells per gall (which is correlated with gall diameter and gall weight) showed that in U. cardui there is mutual facilitation rather than larval competition. Increasing numbers of larvae per gall led to a decreasing mortality and increasing larval weight. Larval weight in turn was positively correlated with the probability of survival to adulthood and with adult weight and fecundity. Thus, all fitness parameters measured favoured large galls. Clutch sizes in oviposition experiments were distinctly larger than the number of gall cells of field populations and in cage experiments, suggesting high mortality of eggs and/or early larval instars. There was a significant relationship between the internal structure (i.e., the size of the growing point) of the bud and clutch size, suggesting that U. cardui females are able to measure bud quality and adapt clutch sizes accordingly. Clutch size was positively correlated with the female's age at first oviposition and negatively with the number of previous ovipositions and previously laid eggs. Since the potential egg capacity per female is higher than the average number of larvae it is likely to produce during its short adult lifespan, U. cardui females tend to be time-limited rather than egglimited, which might favour large clutches once an appropriate oviposition site has been located. As the development of the gall and hence the fate of a clutch depends on a number of unpredictable factors, exclusive concentration of eggs in a few large clusters would involve risks which could be avoided by increasing the number of clutches. Therefore we interpret the high variation of clutch sizes in U. cardui as a mixed strategy of bet hedging and gambling.

Infection status with the metacercariae of heterophyid flukes in the brackish water fish from Haenam-gun, Chollanam-do, Korea

An epidemiological survey was performed to know the infection status of heterophyid fluke metacercariae in the brackish water fishes purchased from a local market in Haenam-gun, Chollanam-do, Korea from November to December, 1991. A total 20 out of 30 shads (Konosirus punctatus) examined were infected with the metacercariae of H. continua (average number of larvae per an infected fish: 2.7). Of 20 perches (Lateolabrax japonicus), 19 were infected with the metacercariae of H. continua (average number per an infected fish: 17.2). Of 30 mullets (Mugil cephalus) examined, 11 were infected with the metacercariae of H. nocens (average number per an infected fish: 51.5), 10 mullets harboured 31 and 349 metacercariae of P. summa and S. fuscatum respectively. Of 30 gobies (Acanthogobius flavimanus) examined, 3 were infected with the metacercariae of H. nocens (average number per an infected fish: 32.0), 8 with those of H. continua (average number per an infected fish: 12.6) and 3 with those of S. fuscatum. From the above results, it has been confirmed that the brackish water fish from Haenam-gun, Chollanam-do are infected with numerous metacercariae of H. nocens, H. continua, P. summa and S. fuscatum.

Warble infestations in some Canadian caribou and their significance

Warble fly larvae (Oedemagena tarandi) occurred in 97-100% of barren-ground caribou (R.t. groen-landicus) sampled in March from the Beverly herd. In December, they occurred in 98% of males and 75% of females. Larvae numbers increased up to several-fold from December to March. Within age classes, males generally were more heavily infected than females. Annual differences were small. Larvae occurred in 14 and 26% of two populations of Peary caribou (Rangifer tarandus pearyi) on the Canadian Arctic Islands. In them, incidences of larvae were unrelated to sex or age. Greater than average numbers of larvae in barren-ground caribou sometimes were associated with females in relatively poor condition and therefore less fecund. These results are discussed in relation to current hypotheses of the factors that affect warble infections.

Resistance to potato cyst nematodes,Globodera spp., in wild and primitiveSolanum species

This paper summarizes the results, up to June 1986, of screening the Dutch-German potato collection at Braunschweig Genetic Resources Centre (BGRC) for resistance toGlobodera pallida andG. rostochiensis virulence groups. Resistance toG. pallida was detected in 4.1 of the 78Solanum species tested. The number of accessions with a pathotype-specific high-level resistance was high but accessions with resistance to allG. pallida andG. rostochiensis virulence groups were rare. Four accessions had a high level of resistance to all virulence groups and 26 had partial resistance. The partially resistant genotypes differed in the average number of larvae per root and of eggs per cyst.

Recent Demonstration Of Helminth Eggs And Larvae From Vegetable Cultivating Soil.

A survey on soil samples collected from the vegetable gardens and vinyl houses in the vicinity of Taegu was conducted for the discovery of helminth eggs and larvae from October 1981 to September 1982. The samples collected were examined utilizing the "Commonly Employed" and Kamiya's techniques. The details of comparative features of larval nematodes are taken from the handbook of parasitology by Matsubasyhi et al. (1965). The results were compared with the data obtained from soil samples collected at the same area by Lee(1976). Five kinds of helminth eggs, ascarid, hookworm, liver fluke, Trichostrongylidae, and whipworm and undetermined eggs were found. Of these, the incidence of ascarid eggs was found to be the highest, 70.5 per cent, followed by whipworm and hookworm eggs, 9.9 and 9.2 per cent, respectively. The average number of ascarid eggs per 100 grams of soil was higher in the vinyl houses, compared with the number in the vegetable gardens than in the vinyl houses. By contrast, the number of hookworm eggs was relatively high in the vegetable gardens. In the monthly incidences of helminth eggs, ascarid eggs were found every month, continuing fairly high incidences all the year round. However, hookworm eggs was found for 8 months from February and September, with low monthly incidences between 4.0 and 22.2 per cent, and Trichostrongylidae eggs were found for 6 months from April to September, with lower incidences than those of hookworm. Three kinds of larval nematodes, the filariform and rhabditoid larvae of hookworm, Trichostrongylidae, and undetermined larvae were found in the soil of farms, but the incidences of larvae were quite low. The average number of larvae per 100 grams of soil was 0.05. When the number of eggs per 100 grams of the soil in 1976 were compared with 1982, pronounced reduction of the number was encountered in all helminth eggs. However, the incidences and the average number of larvae per 100 grams of the soil were so low that it was impossible to compare the data between 1976 and 1982.