Field comparisons of attractants for the screwworm fly (Diptera: Calliphoridae) in a tropical dry forest in Costa Rica.

Field trials were conducted to determine the best attractant for adults of the screwworm, Cochliomyia hominivorax (Coquerel), in Costa Rica. The five attractants were wounded sentinel sheep, decayed fruit, rotted beef liver, rotted fish, and medium used to rear larvae of this blow fly. Significantly more adults came to rotted liver than any other attractant. No adults were captured in traps baited with rotted fruit. Significantly more males came to beef liver than were captured at other baits; males were rarely encountered at wounds. Ovarian development of females obtained with different attractants indicated that proportionally more gravid females visited wounded animals than were caught in traps with proteinaceous baits. Most females had mated by egg stage five and mating and and parity in the populations that visited different attractants were similar. Significantly more females (81%) marked initially at wounds returned to wounds than visited traps baited with liver or fish.     

Influence of attractants on behavior of screwworms (Diptera: Calliphoridae) in a tropical wet forest in Costa Rica.

In a mark-release-recapture study, sheep wounds and rotted liver were used as attractants to study movements of the screwworm fly, Cochliomyia hominivorax (Coquerel), in a Costa Rican tropical wet forest in the wet season. When sites were monitored for less than 1 h, liver attracted between 3 and 12.2 times more flies of both sexes than did wounds, but proportionately fewer gravid and parous females. Only 24.6% of females marked at liver sites were recaptured; seldom (3.1%) did they visit sheep wounds. Females originally marked at sheep wounds remained at the study site longer, visited both sheep and liver sites, and greater than 50% were recaptured. Some females were observed for 16 d and one laid four clutches of eggs. Only 8% of the marked males were recaptured and none was recaptured less than 2 d later. Only a small proportion of the adult screwworms at a locality visited wounds on sentinel sheep; the majority of the adults were transient.     

Sentinel eggs underestimate rates of parasitism of the exotic brown marmorated stink bug,Halyomorpha halys

Native to eastern Asia, the brown marmorated stink bug (BMSB), Halyomorpha halys (Stål), has become a serious invasive pest in North America. Consequently, accurate assessment of parasitism rates under field conditions is critical for determining baseline parasitism rates of native egg parasitoids on BMSB, and for future evaluations of native or exotic parasitoid biological control release strategies and impacts. BMSB sentinel (laboratory-laid) egg masses have typically been used for this purpose, even though they could be providing misleading estimates of parasitoid activity. Accordingly, we compared the use of BMSB sentinel (laboratory-laid) and wild (naturally field-laid) egg masses in 2012 and 2013 to examine rates of parasitism and the parasitoid community composition of indigenous egg parasitoids in outdoor ornamental nurseries. Wild egg masses consistently had higher rates of parasitism than sentinel egg masses. In 2012, wild egg masses had a mean percent parasitism of 28.4% compared to 4.6% in sentinel egg masses, while in 2013 the difference between the two methods increased even further with a mean percent parasitism of 55.3% in wild egg masses compared to 0.8% in sentinel eggs. Furthermore, we found greater total numbers of parasitoids (889, 42) and greater species richness (seven, five), when using wild egg masses compared to sentinel egg masses, respectively. While sentinel egg masses provide a rapid and convenient way to assess the presence of natural enemies, our findings indicate that using sentinel egg masses could dramatically underestimate actual rates of parasitism and provide inaccurate estimates of parasitoid community composition. Future studies should address potential mechanisms underlying these patterns such as lack of certain host cues required by parasitoids in sentinel compared to wild egg masses.     

Effectiveness of gypsy moth mating disruption from aerial applications of plastic laminate flakes with and without a sticking agent

1 The plastic laminate flake formulation, Disparlure II, is currently the only gypsy moth mating disruption product available for aerial application. The elimination of a sticking agent from the formulation would reduce costs, simplify application, and make it possible to apply the product without specialized equipment. 2 A test was conducted in wooded plots in Virginia during 1997 and 1998 to determine whether a sticking agent is necessary. Treatment effectiveness was assessed from the rates of male moth capture in pheromone‐baited traps and mating success of both laboratory‐reared and wild females. 3 Male moth capture was reduced 75.6 and 92.9% in plots treated with flakes without and with a sticking agent, respectively. The percentage of mated females that produced egg masses with more than 5% fertile eggs was reduced by 86.3 and 99.5% in plots treated with flakes without and with a sticking agent, respectively. 4 Moth capture and mating success of laboratory‐reared females did not differ significantly between plots treated with flakes with and without a sticking agent. However, the consistently greater reduction in mating success in both years provides strong evidence that mating disruption is less effective when flakes are applied without a sticking agent. The proportion of wild egg masses collected in 1998 with more than 5% fertile eggs was significantly higher under the no‐sticking agent treatment. 5 In special situations where the use of a sticking agent may be problematic, such as in residential areas, the data indicate that a high level of mating disruption is likely to occur even without the use of a sticking agent.     

Evaluation of Aprostocetus hagenowii (Hymenoptera: Eulophidae) for the control of American cockroaches (Dictyoptera: Blattidae) in sewers and crevices around buildings

The objective of this study was to evaluate the potential of Aprostocetus hagenowii (Ratzeburg) (Hymenoptera: Eulophidae) to control American cockroaches, Periplaneta americana (L.) (Dictyoptera: Blattidae), in sewer manholes and in crevices around buildings. Parasitoids were released weekly for 12 wk from laboratory parasitized heat-killed oothecae, and parasitism monitored using sentinel oothecae of American cockroaches. In addition, preference of A. hagenowii for 1- to 4-wk-old oothecae was evaluated in the laboratory. A. hagenowii females showed no preference for any ootheca age. Twenty of the 30 tested females parasitized one ootheca, whereas the other 10 parasitized two oothecae. The total progeny (males, females, and total) that emerged from a single ootheca parasitized by a female was not significantly different to the total progeny that emerged from two oothecae parasitized by a female. The number of males, females, and total progeny that emerged from the second parasitized ootheca was significantly less than the number that emerged from the first parasitized ootheca. The weekly mean sentinel oothecal parasitism rate in wall crevices was 18.1 +/- 3.2% and in sewer manholes was 13.3 +/- 2.0%. The mean number of released A. hagenowii females per number of parasitized sentinel oothecae recorded in crevices was 189 +/- 18, whereas it was 428 +/- 50 in sewers. A. hagenowii females were more effective at parasitizing sentinel oothecae placed at high and middle levels in manholes than at a low level when releases were made at the midpoint of the manhole shaft.     

Reproductive biology of Fidiobia dominica (Hymenoptera: Platygastridae), an egg parasitoid of Diaprepes abbreviatus (Coleoptera: Curculionidae)

The reproductive biology of Fidiobia dominica Evans (Hymenoptera: Platygastridae) was studied in the laboratory (25.6 +/- 1 degrees C) using host eggs of Diaprepes abbreviatus L. (Coleoptera: Curculionidae). F. dominica readily parasitized D. abbreviatus eggs on both host plant and wax paper substrates. The number of egg masses parasitized and the number of offspring produced were higher when females were offered more than one host egg mass but did not differ when either two or three egg masses were offered. Female parasitoids that were provided with host eggs and a honey food source lived significantly longer than those that were not provided a food source; however, they did not parasitize more D. abbreviatus eggs. Oviposition occurred in host eggs from 0 to 7 d old, and host mortality was relatively consistent for eggs 0-5 d old and lower for eggs 6-7 d old. Successful parasitoid emergence seldom occurred after host eggs were 4 d old, and by 7 d, no adults successfully emerged. Developmental time from egg to adult was 19.3 +/- 0.2 d for males, significantly more rapid than the females (20.4 +/- 0.1 d). The mean longevity of adult females was 8.0 +/- 0.4 d, with a mean oviposition period of 2.7 +/- 0.3 d; males survived 8.1 +/- 0.4 d. The demographic parameters including intrinsic rate of increase (r(m)), generation time (T), and net reproduction (R(o)) were 0.142/d, 22 d, and 22.4 female eggs/d, respectively.     

Dispersal of the Old World screw-worm fly Chrysomya bezziana

Abstract. Dispersal of the Old World screw-worm fly, Chrysomya bezziana Villeneuve, was studied in Papua New Guinea by releasing radio-isotope labelled, laboratory-reared flies and collecting their labelled egg masses from sentinel cattle. A log-linear model was developed to describe recapture rate. Distance was found to dominate the model and was represented by a bilinear ('broken-stick') term as log-distance. Further terms in the model such as attractiveness of the site (estimated from the number of non-labelled egg masses), the season of the year and a time trend were statistically significant but of minor importance. From the model, the median distance females dispersed before depositing an egg mass was 10.8 km. The maximum distance from the release site that egg masses were recovered was 100 km.
The dispersal ability of C. bezziana is discussed in terms of its impact on the prospects of eradicating this species using SIRM if an outbreak occurred in Australia.     

Current status of the New World screwworm Cochliomyia hominivorax in Venezuela

Abstract.  The geographical distribution and seasonality of the New World screwworm (NWS), Cochliomyia hominivorax Coquerel (Diptera: Calliphoridae), were monitored through the use of sentinel animals as part of a co-ordinated programme involving veterinarians and farmers, as well as undergraduate students and teachers from veterinary colleges in Venezuela. This surveillance activity made it possible to collect NWS egg masses or larvae from all 23 states in the country and to determine that the rainy season has a strong positive influence on the number of cases of myiasis caused by C. hominivorax in dogs. In addition, efforts were made to obtain the co-operation of the public health service in order to document the extent of human myiasis in the western–central region of Venezuela. Preliminary results revealed 241 cases over a 7-year period, with cases reported in infants as well as in elderly people. Larvae causing myiasis, other than C. hominivorax , were collected from primary myiasis in rabbit ( Lucilia eximia [Wiedemann]), dog (an unidentified sarcophagid species), birds ( Philornis sp.) and wild mice ( Cuterebra sp.). The economic impact of NWS in Venezuela has not been calculated in terms of loss of milk and meat production, damage to hides or death of animals. Control costs (e.g. cost of larvicides) have been estimated at US$ 2 m per year. Control of myiasis in animals is achieved through the use of chemical compounds, mainly organophosphorus (OP) compounds, macrocyclic lactones and, more recently, a foamy spray based on spinosad. Concerns about insecticide resistance to OP compounds have been raised.     

Monitoring adult populations of the screwworm (Diptera: Calliphoridae) with feeding stations baited with liver.

Populations of the screwworm, Cochliomyia hominivorax (Coquerel), were monitored by capturing adults with hand nets and rooted liver set on the ground. Adults were marked and released. During the 61-d study conducted in a tropical dry forest in the dry season (January to March 1989), 2,640 individual females and 460 individual males were recorded at the four liver-baited stations. The total number of visits by females was 5,769 and by males 510. The mean number of unmarked adults per day was 44.1 females and 7.6 males in an area of approximately 2.59 km2. The mean percentage of marked flies that were recovered was 64.3%. The mean number of feeding stations visited, times recaptured, and days in the study area by individual females was 2.1, 2.4, and 4.5, respectively. Daily visitational patterns by both sexes at the feeding stations were bimodal with peaks occurring between the hours of 0730 to 0859 and 1500 to 1629. Flies were most active when the mean temperature was 29.9 degrees C; the majority of the visits occurred when air temperatures were between 26 and 33 degrees C. Most females attracted to feeding stations were nulliparous (70.7%) and mated (69.7%). Our results suggest that observing adults at feeding stations is a reliable method of obtaining data on the behaviour and population dynamics of indigenous populations of screwworm adults in tropical habitats. Although this method was labor intensive, the amount of data gleaned from the manipulation of wild populations more than compensated for such costs.     

Laboratory environment effects on the reproduction and mortality of adult screwworm (Diptera: Calliphoridae)

The New World screwworm, Cochliomyia hominivorax Coquerel, is mass reared for screwworm eradication initiatives that use the sterile insect technique. New methods for rearing have helped to reduce the cost of the eradication program. We examined the effect and interaction of three temperatures (24.5, 29.5 and 34.5 degrees C), two diets (2% spray-dried blood plus 0.05% vitamins and corn syrup carrageenan) and three population densities (300, 400, and 500 flies/cage) on egg production, egg hatch, number of observable fertilized eggs, mortality (male and female) and ovarian development. The three population densities did not affect any of the parameters monitored. Using the protein diet increased egg production at all temperatures. Diet did not affect egg hatch or female mortality. Male mortality was significantly greater when fed the protein diet and reared at 24.5 degrees C and 34.5 degrees C. Egg hatch was significantly less when the flies were reared at 34.5 degrees C. When exposed to high temperatures (37 degrees C and 40 degrees C) egg production, egg hatch, fertility and mortality were adversely affected. At the higher temperatures, yolk did not adequately form during oogenesis. When compared to the normal rearing photoperiod (12 L:12 D), short photoperiod (1 L:23 D) increased egg production, egg hatch and fertility but lowered mortality.     

Egg mass destroying behaviour of the female giant water bugLethocerus deyrollei Vuillefroy (Heteroptera: Belostomatidae)

After being laid on emergent aquatic vegetation, the egg masses ofLethocerus deyrollei are brooded by the male. In laboratory studies, females were observed to destroy egg masses and ingest the fluid of eggs. Brooding males fought with these attackers at first, but then gave up the defense and mated with them. After destroying the egg masses, females laid new ones at the same sites on the same night or the following one, and males brooded the new offspring. The population density of this species is very low. Most males engage in brooding and cease to become acceptable mates after most of the females lay the first egg masses. It is costly for females to search out free males in the aquatic vegetation. By destroying egg masses, however, individual females can gain new mates with little exertion and can make them brood their own offspring. Furthermore, the survival of their own offspring increases with the elimination of their competitors.     

Insights into the mating habits of the tiger salamander (Ambystoma tigrinum tigrinum) as revealed by genetic parentage analyses

Among urodeles, ambystomatid salamanders are particularly amenable to genetic parentage analyses because they are explosive aggregate breeders that typically have large progeny arrays. Such analyses can lead to direct inferences about otherwise cryptic aspects of salamander natural history, including the rate of multiple mating, individual reproductive success, and the spatial distribution of clutches. In 2002, we collected eastern tiger salamander (Ambystoma tigrinum tigrinum) egg masses (> 1000 embryos) from a approximately 80 m linear transect in Indiana, USA. Embryos were genotyped at four variable microsatellite loci and the resulting progeny array data were used to reconstruct multilocus genotypes of the parental dams and sires for each egg mass. UPGMA analysis of genetic distances among embryos resolved four instances of egg mass admixture, where two or more females had oviposited at exactly the same site resulting in the mixing of independent cohorts. In total, 41 discrete egg masses were available for parentage analyses. Twenty-three egg masses (56%) consisted exclusively of full-siblings (i.e. were singly sired) and 18 (44%) were multiply sired (mean 2.6 males/clutch). Parentage could be genetically assigned to one of 17 distinct parent pairs involving at least 15 females and 14 different males. Reproductive skew was evident among males who sired multiply sired clutches. Additional evidence of the effects of sexual selection on male reproductive success was apparent via significant positive correlations between male mating and reproductive success. Females frequently partitioned their clutches into multiple discrete egg masses that were separated from one another by as many as 43 m. Collectively, these data provide the first direct evidence for polygynandry in a wild population of tiger salamanders.     

Age distribution of adult female screwworms (Diptera: Calliphoridae) captured on sentinel animals in the coastal lowlands of Guatemala

The age structure of screwworm, Cochliomyia hominivorax (Coquerel), populations was studied in the Guatemalan lowlands with the pteridine technique of age determination. Flies (95% were 4-15 d old) were captured on sentinel animals. Mean age was 7.5 d. The oldest fly captured was 21 d old. Most flies visiting wounds were reproductively mature females. Of these, about one-half oviposited once, one-third oviposited twice, and 1 in 10 completed three ovarian cycles (assuming a 3-d interval between clutches). Periodicity in adult capture rates may be related to the reproductive cycle. Results suggest that local populations are composed of a high proportion of synchronized cohorts.     

Seroprevalence of six reproductive pathogens in European wild boar (Sus scrofa) from Spain: the effect on wild boar female reproductive performance

We studied the seroprevalence of six reproductive pathogens in Spanish hunter-harvested wild boar females. The sample was representative of the hunting harvest in the studied hunting estates. Mean antibody prevalences were: 60.6+/-0.06% for Aujeszky's disease virus (ADV), 56.6+/-0.09% for porcine parvovirus (PPV), 51.8+/-0.06% for porcine circovirus type 2 (PCV2), 29.7+/-0.09% for Brucella spp. and 36.3+/-0.1% for Toxoplasma gondii. We did not detect antibodies against porcine reproductive and respiratory syndrome virus (PRRSv). ADV seroprevalence was associated with PPV and PCV2 seroprevalence in Spanish wild boar females. Ovulation rate in the studied wild boar females was 4.41+/-0.16 (n=120), mean litter size was 3.91+/-0.16 (n=82) and the partial resorption index 0.92+/-0.17 (n=66). Ovulation rate and litter size were statistically associated with age. T. gondii seroprevalence was negatively related to ovulation rate and partial resorption index. Wild boars from managed fenced estates had antibodies against more pathogens than wild boars from open estates. Potential relations between management of wild boar populations and exposure of individuals to different reproductive pathogens are discussed.     

A new meatless diet for adult screwworm (Diptera: Calliphoridae)

Screwworm flies, Cochliomyia hominivorax (Coquerel), were fed on honey and spray dried egg product; honey, molasses, and spray dried egg product; honey and spray dried meat protein; as well as on a control diet of honey and horsemeat, which is the standard diet used for screwworm adult colony in the mass-rearing facility. In general, the weight of eggs laid by females fed on the diet of spray dried egg product was significantly higher than that laid by females fed on the standard horsemeat diet. Egg production declined when spray dried meat protein replaced the egg product. Partial replacement of honey with molasses in the egg diet did not decrease egg production, compared with the control diet. The use of spray dried egg diet has advantages over the horsemeat diet, such as storage, handling, preparation, feeding, and expense. A cost analysis suggests that replacing the horsemeat with spray dried egg product, and half of the honey with molasses, would reduce the cost of the diet by more than US $100,000 annually.     

Crop-specific mortality of southern green stink bug eggs in Bt- and non-Bt cotton,soybean and peanut

Increasing insecticide use against stink bugs erodes benefits accrued to cotton production in the southeastern USA by eradication of the boll weevil and widespread use of Bt-transgenic cotton. Biological control programs designed to mitigate the impact of these pests would be beneficial; therefore, we sought to identify and assess naturally occurring biological control agents of stink bug eggs in cotton, peanut and soybeans, three important crops and stink bug hosts in the region. Two studies were conducted utilising digital imaging of sentinel egg masses to capture enemies present and sequential imaging over time to characterise the type and amount of damage inflicted on the egg masses. The first study utilised plots of soybean, Bt cotton, non-Bt cotton and peanut. The second study focused on ant predation in cotton by excluding fire ants from half of the plots. Sentinel egg masses of the southern green stink bug were placed in all plots at weekly intervals and were photographed at placement and at intervals over 72 h. Surviving egg masses were collected and held in the laboratory to assess parasitism in the first study. Predation of eggs was high in peanut (74–86%) and soybean (39–65%), and lower in Bt (26–34%) and non-Bt (4–21%) cotton over the two years. Parasitism was low overall (0.17–19.0%). Most egg predation in cotton and peanut was attributable to fire ants, whereas long-horned grasshoppers dominated in soybean. Exclusion of fire ants in cotton significantly reduced egg mortality, indicating their predominance as mortality agents in cotton.     

Oviposition strategies employed by the western spruce budworm: tests of predictions from the phylogenetic constraints hypothesis

1 Predictions from the Phylogenetic Constraints Hypothesis were tested for the first time in an eruptive forest Lepidopteran species, the western spruce budworm. 2 In previous work, we established that western spruce budworm females exhibit oviposition preferences with regard to tree age, tree vigour and host species. However, there was no evidence to support a link between oviposition preference and larval performance, which supports the Phylogenetic Constraints Hypothesis. 3 Our preference data led us to test whether female budworms use oviposition strategies to select the sites where they lay their egg masses. Our experiments were designed to make direct comparisons between latent and eruptive insect herbivores with respect to two oviposition behaviours: egg retention and avoidance of conspecifics. This type of research has not previously been conducted on any eruptive forest Lepidopteran. 4 Female budworms retained eggs instead of laying them on less preferred hosts in two of three experiments, but the percentage of eggs they retained was significantly less compared to latent insect herbivores. 5 In addition, female budworms actively avoided oviposition in areas with the highest density of conspecific egg masses, but they laid egg masses in all the other locations provided. This contrasts with the pattern seen in latent insect herbivores, which consistently avoid laying their eggs near any sites already used by conspecifics. 6 Our research indicates that there are extreme differences between latent and eruptive insect herbivores with respect to egg retention and avoidance of conspecifics, thus supporting the Phylogenetic Constraints Hypothesis.     

Colonization and bionomics of the sandfly Phlebotomus kazeruni from Sinai, Egypt

Phlebotomuius kazeruni (Diptera: Psychodidae) females were collected by light-trap in southern Sinai, Egypt, and this sandfly species was colonized for the first time as a laboratory strain, maintained by the procedures of Modi & Tesh (1983). Laboratory-reared females did not lay eggs autogenously; they blood-fed more readily (P=0.02) on a hamster (37%) than a human (22%) during 1 h exposure. Fecundity of hamster-fed females was significantly greater than for those fed on human blood: 69.4 +/- 5.8 vs. 45.2 +/- 8.1 eggs/female from the first gonotrophic cycle. Pre-oviposition and egg incubation periods were significantly less for females fed on hamster compared with human blood, but the larval development and pupation periods were not affected by this difference in bloodmeal source. Egg to adult survival was equivalent (38%) for progeny of females blood-fed on hamster or human. The mean generation time of progeny from females fed on hamster (51.9 +/- 1.0 days) or human (53.3 +/- 1.7 days) was not significantly different. The sex ratio of adult male:female progeny was similar (P=0.2) for both hosts: 42:58% from hamster, 46:54% from human blood-fed female parents. Evidently P. kazeruni from Sinai is sufficiently anthropophagic to be a potential vector of Leishmania from rodents to humans.     

The screw-worm flyChrysomya bezziana villeneuve (Diptera: Calliphoridae) in a sterile insect release trial in Papua New Guinea

The feasibility of the sterile insect release method (SIRM) was tested against natural populations of the Old World screw-worm fly, Chrysomya bezziana in the Musa Valley, Papua New Guinea. Sterile mating frequencies were determined from egg masses laid by native females on wounded, sentinel cattle. The aerial release of sterilised puparia resulted in low frequencies of sterile matings and few trap recaptures of released material. The release of chilled adult flies resulted in higher frequencies of sterile matings and many trap recaptures. The mean density of males released was 230 males per km² per week over a target area of 361 km² (48% of the valley). Sterile masses were first detected 2 weeks after the release of chill flies commenced, reaching a weekly peak of 33% after 5 weeks of releases with 15% of egg masses found to be sterile during the final month. The levels of sterile matings achieved in this trial were similar to comparable SIRM studies made in the USA, Mexico and Guatemala to control the New World screw-worm fly, Cochliomyia hominivorax.     

Mean life expectancy of Old World screwworm fly,Chrysomya bezziana,inferred from the reproductive age-structure of native females caught on swormlure-baited sticky traps

Abstract. The reproductive status of native (wild) screwworm fly, Chrysomya bezziana, caught on swormlure-baited sticky traps in Papua New Guinea is described. A total of 1122 females and 25 males were trapped. Of these females 595 were scored for insemination status and stage of ovarian development (on a scale of 2–10) of which 20% were in suitable condition for assignment to first, second and third ovarian cycles. Of the nulliparous females, only 17% were inseminated at stage 3 of ovarian development, 70% at stage 4, 93-97% at stages 5 and 6, and all of stages 7–10 (gravids). All parous females were inseminated. More than half of the captured females were parous (58%) and only 7% of the total were gravid. Proportions of females in ovarian cycles 1, 2 and 3 were 41%, 50% and 9% respectively. Survival of female Ch. bezziana in the laboratory was adequately described by lognormal and Gompertz survival functions, for both of which the mortality rate is an increasing function of reproductive age. Analysis of the reproductive age distribution of native females estimated their mean life-expectancy at 9 days under the prevailing mean field temperature of 26.5^oC. This equates to completion of 1.7 ovarian cycles and an estimated mean lifetime fecundity of 146 female progeny. The survival models, which also allowed responsiveness of females to swormlure-baited traps (female trappability) to vary according to their stage of ovarian development, indicated significant age-dependent trapping bias. These findings are compared with similar data for the New World screwworm fly, Cochliomyia hominivorax.