Egg Mass Deposition Research Articles

Seasonal activity of spotted lanternfly (Hemiptera: Fulgoridae), in Southeast Pennsylvania.

The spotted lanternfly, Lycorma delicatula (White, 1845), is an invasive species in the United States. This pest causes damage to vineyards and has the potential to negatively affect other crops and industries. Information describing the seasonal timing of life stages can improve its management. In 2019 and 2020, spotted lanternfly seasonal activity was followed weekly from spring egg hatch to the first hard freeze. Weighted mean timing of activity for each nymphal instar, early adults, late adults, total adults, and egg mass deposition are presented for 2019 and 2020 on Acer rubrum and 2020 on Ailanthus altissima. Logistic equations describing the percentage completion of each activity period on these hosts were fitted using a start date of 1 January to calculate accumulated degree days (ADD). For the adult and egg mass deposition periods, we additionally used a biofix of the date adults were first observed to calculate ADD. ADD from 1 January adequately estimated the timing of nymphal instars but ADD from observation of the first adult better estimated the timing of adult activity and egg mass deposition. Late adult activity and egg mass deposition periods appeared to be influenced by another environmental cue, such as day length. Maps of season-long ADD show that spotted lanternflies are unlikely to reach adulthood in colder regions of the northeast United States, and therefore may not establish there. We also report a strong seasonal trend in sex ratio on A. rubrum, where the population shifted from over 80% male to over 80% female in October.

Toxic, cytotoxic and genotoxic effect of saline extract and fraction of Parkia pendula seeds in the developmental stages of Biomphalaria glabrata (Say 1818 – intermediate host) and cercaricide activity against the infectious agent of schistosomiasis

This study describes for the first time the effect of saline extract and Parkia pendula seed fraction on Biomphalaria glabrata adult embryos and molluscs well as the reproductive parameters (fecundity and fertility) and survival, in addition to cytotoxicity and genotoxicity through the profile of blood cells after exposure to sublethal concentrations. Furthermore, we analyzed the action of both preparations against the cercariae of Schistosoma mansoni and their environmental safety using the bioindicator Artemia salina. The saline extract and fraction showed toxic effects for embryos (CL90 of 464.25, 479.62, 731.28, 643.28, 408.43 and 250.94, 318.03, 406.12, 635.64, 1.145 mg/mL, for blastula, gastrula, trocophore, veliger and hippo stage respectively), adult snails after 24 h of exposure (CL90 of 9.50 and 10.92 mg/mL, respectively) with increased mortality after 7 days of observation and significant decrease (p <0.05; p < 0.01 and p < 0.001) in egg mass deposition. At sublethal concentrations, an increase in quantitative and morphological changes in hemocytes was observed, and in the genotoxicity/comet assay analysis, varying degrees of nuclear damage were detected. In addition, the saline extract showed changes in the motility of the cercariae, while the fraction howed toxicity from a concentration of 1.0 mg/mL. The saline extract showed toxicity to A. salina at the highest concentrations (3.0, 4.0 and 5.0 mg/mL), while the fraction did not show ecotoxicity. Thus, the saline extract and fraction was promising in combating schistosomiasis by eliminating the intermediate host and causing alterations and/or mortality to the infectious agent.

Life-history traits display strong associations to genome size in annelids

Genome size, known also as the C-value, has been proposed as an important determinant of life-history variation in numerous animal taxa. We assessed the relationships between genome size and fitness-related life-history traits in six species of interstitial marine annelids of the genus Ophryotrocha. Life-history traits and genome size data obtained from 18 additional annelid species were included in our analyses to have a broader phylogenetic scope. Unexpectedly, genome sizes assessed here by flow cytometry in four Ophryotrocha species were three times larger than previously reported values obtained using Feulgen densitometry. This has implications for the hypothesis that harsh interstitial habitats select for small genomes in meiofaunal annelids. Within the genus Ophryotrocha, significant and positive relationships were found between genome size and nucleus size, and between genome size, age at first egg mass deposition, body size and lifespan. These relationships held up in the broader phylogenetic comparison. Our study provides evidence for the important role played by genome size in the evolution of life-history traits in annelids.

Abyssal demersal fishes recorded at station M (34°50′N, 123° 00′W, 4100 m depth) in the northeast Pacific Ocean: An annotated check list and synthesis

The demersal ichthyofauna at the abyssal Station M at 4100 m depth in the NE Pacific Ocean (34°50′N, 123° 00′W) has been sampled from 1989 onwards using a combination of techniques; baited traps, long lines, otter trawls, towed camera sledge, remotely operated vehicles (ROV), human occupied vehicle (Alvin), benthic long-term time lapse camera and baited camera landers. The fish fauna is dominated by two species of macrourid Coryphaenoides armatus and C. yaquinae. Other species present are Bathysaurus mollis (Bathysauridae), Coryphaenoides leptolepis (Macrouridae), Bassozetus nasus, Spectrunculus grandis (Ophidiidae), three species of Liparidae, including Genioliparis ferox and a Zoarcid (Pachycara sp.). Evidence of deposition of egg masses by snail fishes, liparids on oceanographic equipment is discussed.

In situ Monitoring of Longfin Inshore Squid Egg Deposition and Embryonic Development

Knowledge of squid early life history is relatively poor despite its importance for fisheries management. The longfin inshore squid Doryteuthis pealeii (Lesueur, 1821) is a commercially important species harvested extensively along the northeastern United States continental shelf. To understand the effects of fishing and environmental variability on D. pealeii in an inshore spawning ground (Nantucket Sound, MA), egg deposition and embryonic development were monitored in situ at commercial fish weirs in spring and summer 2008 to 2016. Logbooks were maintained in which catch (including the presence of egg masses) and effort data for each weir were recorded daily. Seawater temperature was recorded using data loggers affixed to the weirs. Newly deposited egg masses were transferred to a mesh enclosure on an opportunistic basis and placed immediately adjacent to the weir to permit semiweekly retrieval and sampling. Samples (five randomly chosen “fingers” excised from a mass) were chilled and transported to a nearby wet lab for microscopic examination to determine embryonic development stage. Hatch timing was determined via direct observation of paralarvae emerging from egg masses and development time was calculated as the number of days between egg mass deposition and hatching. The timing and duration of egg mass deposition varied between years. Embryonic development time of 15 egg masses ranged from 12 to 34 days and generally decreased at warmer temperatures. In situ observations were consistent with the findings of laboratory studies of D. pealeii and other loliginid squids.

Natural egg mass deposition by the Humboldt squid (Dosidicus gigas) in the Gulf of California and characteristics of hatchlings and paralarvae – ERRATUM

Natural egg mass deposition by the Humboldt squid (Dosidicus gigas) in the Gulf of California and characteristics of hatchlings and paralarvae – ERRATUM

Spawning Behavior of Lingcod in the Seattle Aquarium

Lingcod (Ophiodon elongates) are members of the family Hexagrammidae and are found in the northeast coastal waters of the Pacific Ocean. Hexagrammids are demersal spawners with the male fish guarding eggs until hatching occurs. The spawning behavior of Lingcod has only been observed and described once in the literature (Wilby 1937). Although other investigators have described various aspects of Lingcod life history and reproductive activity (for example, Jewell 1968; Low and Beamish 1978; LaRiviere and others 1981; Giorgi 1981; Cass and others 1990; Jagielo 1994), none directly observed spawning. Withler and others (2004) genetically evaluated progeny and documented polygamous mating by Lingcod. This note describes a Lingcod spawning event in the Seattle Aquarium and compare this spawning to that described previously by Wilby (1937). The Underwater Dome exhibit of the Seattle Aquarium is in the form of an igloo-like public observation volume immersed in a large cylindrical vessel. The vessel is approximately 20 m in diameter and 6 m deep, containing more than 1800 m of filtered seawater pumped from adjacent Elliot Bay, in an open system with the water discharged back to the bay. The surface of the vessel is not enclosed, and is protected by an awning covering a portion of the water surface. Environmental conditions inside the exhibit, such as temperature and lighting, match ambient conditions. A low-light level is maintained in the exhibit at night. The exhibit topography mimics rocky and nearshore habitat conditions found in the Salish Sea. The highrelief rocky reef structure is made of concrete, and the bottom is covered with a shallow layer of coarse beach sand. The exhibit is home to a variety of fish and invertebrate species found in local waters. The animals are fed a variety of fish and shellfish similar to their natural diet. The Lingcod feed primarily on forage fish and squid, and occasionally prey on smaller exhibit fish, usually salmonids. Lingcod in the exhibit typically spawn each season between mid-December and mid-March, usually near year-end, using one or more of 3 specific locations. Characteristics of the 3 sites are consistent with sites selected by fish in the wild (KWJ, pers. obs.), distinguished by rocky reef ledges with deep cracks or crevices suitable for deposition of egg masses, supporting the premise that physical characteristics of the exhibit are conducive for display specimens to behave and reproduce in near-natural conditions. The site of the observed spawning is an approximately parallel-sided cavity 20 cm wide between a flat-sided boulder and a vertical reef surface. The site is about 2 m from viewing windows. The dome exhibit was home to 5 adult Lingcod ranging from 75to 110-cm total length at the time of the observed spawning. Two of the fish were known to be female and 2 were known to be male. The sex of the 5th fish was unknown. The ages of the fish were also not known. Observations were visual and notes were made after the event. Measurements were made using a 1-m-long plastic tube graduated in 10-cm increments. On 1 January 2015, a pair of Lingcod spawned in the Underwater Dome exhibit of the Seattle Aquarium. The spawners were the largest female and largest male in the exhibit. The female was gravid and swollen to the point of concern by aquarium staff that she was egg-bound. The site selected by the spawners was the site most frequently used for egg laying in previous years. The male fish had established long-standing dominance of this site during the spawning season by remaining at the location, performing courtship display when females were present, and chasing other fish from the area. At approximately 08:30 Pacific Standard Time, in crepuscular conditions, the female Lingcod was observed by a maintenance diver at the spawning location. She was aligned with the cavity with her ventral side up. The fish was alternately squirming and quivering. The male was nearby (Fig. 1A). After an GENERAL NOTES

Survival of brooding females and characteristics of oviposition sites ofUmbonia crassicornis(Amyot &amp; Serville, 1843) (Hemiptera: Membracidae)

Abstract The goals of this study were to 1) determine the field survival rate of single and multiple U. crassicornis females tending their offspring, 2) determine if a female will adopt an egg mass or nyphal aggregation that has lost its parental female as is seen in other treehoppers, 3)determine the physical characteristics of the sites selected by female U. crassicornis for oviposition and 4) show how these data interrelate and explain the pattern of U. crassicornis egg mass deposition within and among the host plants. An average of 27.9% of the female U. crassicornis survived until their offspring reached maturity. Having two or more females at a site doubles the probability of at least one surviving until the offspring reach maturity. An egg mass or nymphal aggregation without a guarding female may be adopted by another female. Females need four to seven cm of plant tissue 2.5 to 3.5 mm in diameter that they can encircle with their mesothoracic legs in which to oviposit. The females do not aggregate ...

Reproduction among protobranch bivalves of the family Nuculidae from sublittoral, bathyal, and abyssal depths off the New England coast of North America

Abstract Protobranch bivalve species of the family Nuculidae pass through either a planktonic lecithotrophic larval stage or a direct non-planktonic development. Oogenesis of the three sublittoral species examined is synchronous. Deposition of egg masses by Nucula delphinodonta and spawning by Nucula annulata and Nucula proxima occur only during summer months. Among the four bathyal and abyssal species, Ennucula similis , Ennucula granulosa , Deminucula atacellana , and Brevinucula verrilli , oogenesis is asynchronous and there is no discernable pattern of periodicity of spawning. Absence of periodicity in reproduction in these deep-sea species is confirmed by examination of individuals from dredge samples taken at different times of the year. The median apparent fecundity among both sublittoral and deep-sea species is directly related to size (i.e. shell length) and age. Among the Nuculidae the median apparent fecundity is greater among sublittoral than bathyal and abyssal species. The geographic distribution of a species depends on its capacity to disperse. The dispersal of the planktonic lecithotrophic larvae of the sublittoral species N. annulata and N. proxima is limited to the continental shelf of the northwestern Atlantic by inshore bottom circulation and because these very small planktonic larvae ( D. atacellana .

Synergistic effects of ultraviolet radiation and conditions at low tide on egg masses of limpets (Benhamina obliquata and Siphonaria australis) in New Zealand

The effects of ultraviolet radiation (UVR), desiccation and conditions in tidal pools on embryonic survival were examined for two common pulmonate limpets that lay intertidal benthic egg masses on rocky shores in New Zealand: Benhamina obliquata and Siphonaria australis. Field surveys and manipulative experiments were conducted between December 2006 and September 2007 in the Wellington region of New Zealand (41°17′S, 174°47′E). Egg mass deposition sites in the field were species-specific: B. obliquata deposited eggs primarily in shaded crevices, whereas S. australis predominantly deposited egg masses in the sun and in tidal pools. For both species, however, embryonic mortality was greater in egg masses that had been in full sun compared to shade. For S. australis, there was also high mortality in egg masses in tidal pools or desiccated compared to those that remained submerged in flowing seawater at low tide. In outdoor experiments, embryonic mortality was also always greatest for egg masses exposed to full sun, and lowest for those in shaded treatments. Mortality was also higher if egg masses were in simulated tidal pools, and for S. australis, if desiccated, compared to those submerged in flowing seawater. Periods of particularly sunny conditions with high temperatures also resulted in higher overall mortality. Finally, egg masses of both species that were initially deposited in the shade had greater mortality in response to subsequent UV exposure compared to egg masses initially deposited in full sun. Results from this study suggest that the egg masses of these two species are highly vulnerable to UVR, as well as other intertidal stressors. Embryos of both of these species may be at risk of high mortality particularly during summer when extreme conditions of UV intensity and high temperature coincide with low tide cycles.

Natural egg mass deposition by the Humboldt squid (Dosidicus gigas) in the Gulf of California and characteristics of hatchlings and paralarvae

The jumbo or Humboldt squid, Dosidicus gigas, is an important fisheries resource and a significant participant in regional ecologies as both predator and prey. It is the largest species in the oceanic squid family Ommastrephidae and has the largest known potential fecundity of any cephalopod, yet little is understood about its reproductive biology. We report the first discovery of a naturally deposited egg mass of Dosidicus gigas, as well as the first spawning of eggs in captivity. The egg mass was found in warm water (25–27°C) at a depth of 16 m and was far larger than the egg masses of any squid species previously reported. Eggs were embedded in a watery, gelatinous matrix and were individually surrounded by a unique envelope external to the chorion. This envelope was present in both wild and captive-spawned egg masses, but it was not present in artificially fertilized eggs. The wild egg mass appeared to be resistant to microbial infection, unlike the incomplete and damaged egg masses spawned in captivity, suggesting that the intact egg mass protects the eggs within. Chorion expansion was also more extensive in the wild egg mass. Hatchling behaviours included proboscis extension, chromatophore activity, and a range of swimming speeds that may allow them to exercise some control over their distribution in the wild.

Temporal patterns of gastropod egg mass deposition on southeastern Australian shores

Spawning of marine invertebrates may be affected by environmental factors (e.g. food availability, environmental stress) or intrinsic factors (e.g. phylogenetic constraints, developmental mode); intrinsic factors may obscure environmental effects. Two-year surveys of gastropod egg mass deposition were conducted at two rocky intertidal sites in south-eastern Australia to test the following hypotheses: (1) temporal patterns of spawning are more similar within taxonomic order than across orders; and (2) species with planktotrophic larvae are more likely to spawn in seasons coinciding with maximum food availability. There were no discernible effects of either order or developmental mode on spawning patterns, suggesting that spawning behaviour is unrelated to taxonomic order or larval food availability. Alternatively, low numbers of species in certain groups may have increased the risk of not detecting significant effects (type II error). Comparisons with anecdotal data from other regions suggest that developmental mode may indeed play a role in marine gastropod spawning. Criteria are provided for future comparative studies, including a direct focus on specific families and the inclusion of similar latitudes and habitats to those used here. Such studies will help to determine the roles of developmental mode, food availability and environmental stress in the evolution of egg mass deposition.

Corrigendum to: Temporal patterns of gastropod egg mass deposition on southeastern Australian shores

Spawning of marine invertebrates may be affected by environmental factors (e.g. food availability, environmental stress) or intrinsic factors (e.g. phylogenetic constraints, developmental mode); intrinsic factors may obscure environmental effects. Two-year surveys of gastropod egg mass deposition were conducted at two rocky intertidal sites in south-eastern Australia to test the following hypotheses: (1) temporal patterns of spawning are more similar within taxonomic order than across orders; and (2) species with planktotrophic larvae are more likely to spawn in seasons coinciding with maximum food availability. There were no discernible effects of either order or developmental mode on spawning patterns, suggesting that spawning behaviour is unrelated to taxonomic order or larval food availability. Alternatively, low numbers of species in certain groups may have increased the risk of not detecting significant effects (type II error). Comparisons with anecdotal data from other regions suggest that developmental mode may indeed play a role in marine gastropod spawning. Criteria are provided for future comparative studies, including a direct focus on specific families and the inclusion of similar latitudes and habitats to those used here. Such studies will help to determine the roles of developmental mode, food availability and environmental stress in the evolution of egg mass deposition.

Experimental control ofBiomphalaria pfeifferi, the intermediate host ofSchistosoma mansoni, by the ampullariid snailLanistes varicus

The biological control of the snail hosts of the trematodes that cause human schistosomiasis appears to be a promising method for achieving sustainable reductions in the transmission of the parasites. The possibility of using the Ghanaian strain of an ampullariid snail, Lanistes varicus, for the biological control of the main snail host of Schistosoma mansoni , Biomphalaria pfeifferi, has now been investigated in laboratory-based experiments. Adult and 2-week-old L. varicus were found to feed voraciously on the egg masses and juveniles of B. pfeifferi (from the Tono irrigation canals in northern Ghana). When single L. varicus were exposed to 20-200 egg masses, they consumed all of the masses over 24 h (if adult) or about 50% of them over 4 days (if 2-week-old juveniles). The effect of the secretions of the ampullariid on the reproduction, growth and mortality of B. pfeifferi was also investigated, by maintaining the two snail species in the same aquarium but separated by nylon netting. The presence of L. varicus in the same aquarium reduced the number of egg masses produced by each B. pfeifferi, although, curiously, the presence of a single L. varicus in the aquarium appeared to have more of an impact, on the egg-mass deposition by 20 B. pfeifferi, than the presence of five or more of the ampullariids. It appears that, under laboratory conditions at least, the Ghanaian stain of L. varicus has the potential to limit populations of B. pfeifferi.

Stimulus-dependent regulation and cellular expression of genes encoding neuropeptides, prohormone convertases, alpha-amidating enzyme and 7B2 in identified Lymnaea neurons.

Synthesis of bioactive peptides is regulated by several post-translational processing events, including cleavage of peptides from a prohormone, and chemical modifications. Using quantitative in situ hybridization and neuron-specific macro-arrays, we first demonstrated cell-type specific expression levels of transcripts encoding prohormone convertases, peptide alpha-amidating enzyme as well as the chaperone 7B2 in Lymnaea neurons. Second, we demonstrated a strict correlation between alpha-amidating enzyme and its neuropeptide substrates. However, this strict relationship of gene expression of the three prohormone convertases and types of cleavage site used is not present. Third, we showed by a physiological stimulus, i.e. clean water, which leads to a stereotyped egg-laying behaviour resulting in successful egg-mass deposition, the co-regulated induction of transcript levels of processing enzymes, 7B2, and egg-laying hormone. These data indicate that (i) these enzymes (and chaperone) are involved in egg-laying hormone neuropeptide biosynthesis, and (ii) neuropeptide release and transcript levels of both prohormones and processing enzymes are regulated in accordance with physiological demands.

Gastropod egg mass deposition on a temperate, wave‐exposed coastline in New South Wales, Australia: implications for intertidal conservation

Abstract The identification and protection of known breeding grounds is a high priority for the conservation of marine biodiversity. Here, we examine the intertidal habitats used by marine gastropods for the deposition of benthic egg masses along a wave‐exposed coastline in New South Wales, Australia. A total of 200 surveys were conducted on 13 intertidal reefs. The egg masses of 46 species were identified, with a further eight distinct types recorded but remaining unidentified. Over half of the gastropods were found to deposit egg masses exclusively on the underside of boulders. Other intertidal substrata used for gastropod egg mass deposition included vertical and horizontal exposed rock surfaces, algal fronds and sand. Only eight species were found to attach their egg masses to more than one type of substratum. Twelve reefs were classified into three categories according to exposure to wave action and habitat diversity. The mean number of species found depositing egg masses was compared using a standard eight surveys from each site. Sub‐maximally wave‐exposed reefs with maximal habitat diversity were found to support a significantly higher species richness of gastropod egg masses, compared with maximally wave‐exposed reefs with either maximal or sub‐maximal habitat diversity (p=0.000). Gastropods that deposit egg masses on the underside of boulders were more likely to be found on sub‐maximally wave‐exposed reefs, whereas species that deposit egg masses in all other microhabitats were equally likely to be found breeding on sub‐maximally or maximally exposed reefs. Gastropods with pelagic larvae tended to occur at a greater number of sites than those that hatch post‐metamorphosis. A significant difference was found between species grouped according to these two developmental modes for the mean number of sites at which egg masses were recorded (p=0.008). Variation in the species richness of gastropods found depositing egg masses on different intertidal reefs appears to be influenced by the availability of suitable boulders and exposure to wave action. These factors should be taken into consideration during the selection of locations for intertidal protected areas. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Location of Beet Armyworm (Lepidoptera: Noctuidae) Egg Mass Deposition within Canopies of Cotton and Pigweed

The beet armyworm, Spodoptera exigua (Hübner), is a sporadic but devastating secondary pest of cotton. Scouting cotton for egg masses is commonly recommended for identifying potential outbreaks and for proper timing of insecticide applications. However, there is disagreement regarding where to look on the plant for beet armyworm eggs. We investigated and quantified placement of egg masses by laboratory colony females within cotton and pigweed (a preferred wild host plant) canopies of different heights. In cotton, almost all egg masses were deposited on the undersides of leaves, and ≈80% of the egg masses were consistently located in the upper 50% of the cotton canopy, and horizontally within the inner 50% of the canopy around the central axis. Although this trend was consistent among all categories of plant height tested, variation about the means decreased with increasing height. A smaller sample of wild females indicated similar vertical placement, but horizontal placement extending further distally in the canopy. Our results indicate that scouting for egg masses on the underside of leaves in the upper half of the canopy will recover ≈80% of the egg masses present on the plants. In pigweed, egg masses were commonly laid within the inner 50% of the canopy, but along the upper 80% of the vertical axis. As in cotton, variation about the means was less in taller plants. The number of eggs per egg mass was 29% less in cotton than in pigweed. This positional information will aid in further efforts to investigate, predict, and manage beet armyworm populations in cotton and noncotton hosts.

Biologia reprodutiva de Euschistus heros (F.) (Heteroptera: Pentatomidae)

Estudou-se a biologia de Euschistus heros (F.) (Heteroptera: Pentatomidae) em laboratório sob 24±0,5ºC, 70±10% UR e fotofase de 14 h. O tempo médio de desenvolvimento até adulto foi de 38,6 d, sendo o 2º estádio ninfal, o de maior índice de mortalidade (10,4%). A longevidade de E. heros variou de acordo com o sexo e atividade sexual. Machos e fêmeas atingiram a maturidade sexual com 11,4 e 11,2 d, respectivamente. O tempo médio para a colocação de posturas, após o primeiro acasalamento, variou de 9,1 d para fêmeas, que acasalaram uma única vez, até 13,9 dias para fêmeas que acasalaram várias vezes durante o período de sobrevivência. O número médio de ovos por fêmea variou de 108,5 até 130,5, dependendo do número de acasalamento das fêmeas estudadas. Juntamente com a deposição das massas de ovos, foi observada a colocação de posturas isoladas com percentagens de 71,7 e 77,8 respectivamente, também dependendo do número de acasalamentos.

Age- and density-related oviposition behavior of the European corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

Age-related oviposition patterns ofOstrinia nubilalis were studied at three population densities in the laboratory by releasing newly eclosed adults in wire-screened cages and analyzing their oviposition throughout the adult stage with digital analysis. Oviposition sequences of individual females depositing egg masses were documented on the third and seventh nights after eclosion with a video camcorder. During a sequence, a female produced an egg in an average time of 15 or 26 s on the third and seventh nights, respectively, and completed depositing an egg mass the size of 20–39 eggs in an average time of 316 and 525 s, respectively. Females were not easily disturbed during egg mass deposition and pulsated their abdomen before deposition of each egg. Females produced few egg masses the first night after eclosion. Oviposition increased on nights 2 and 3 but declined steadily thereafter as females matured. Females older than 6 nights produced fewer egg masses; the proportion of egg masses with fewer than 20 eggs increased gradually. By the end of the adults' lifetime, nearly 100% of the egg masses had fewer than 20 eggs. The data are fundamental to our research to define the role of phytochemicals in modifying oviposition behavior of the European corn borer.

Evaluation of Trichogramma nubilalis and Bacillus thuringiensis in Management of Ostrinia nubilalis (Lepidoptera: Pyralidae) in Sweet Corn

A biological control program for European corn borer, Ostrinia nubilalis (Hubner), using Trichogramma nubilalis Ertle & Davis and Bacillus thuringiensis var. kurstaki was tested in plots of sweet corn 1990 and 1991. Trichogramma were released during the egg mass recruitment period of O. nubilalis to bracket the peak egg mass deposition period. One or two B. thuringiensis applications were targeted against host larvae that escaped T. nubilale parasitism in the egg stage. The European corn borer phenology model adequately predicted the timing and shape of the adult flight and egg recruitment periods in 1990 and 1991. The released Trichogramma parasitized 70 and 56% of the European corn borer eggs in 1990 and 1991, respectively. In both years, < 20% of the host eggs hatched in the Trichogramma release plots, compared with 38-56% in the control plots. Total mortality of European corn borer from egg deposition to sweet corn harvest was 94 and 92% in 1990 and 1991, respectively. The stage structure of the European corn borer population at sweet corn harvest in 1991 did not differ between the Trichogramma release and no release plots. The proportion of sweet corn ears free of European corn borer larvae varied with position of the plots relative to nearby sudangrass, and ranged between 0.7 and 0.9 in the release plots, compared with 0.6- 0,65 in control plots in 1990 and 1991, respectively