Egg Clusters Research Articles

Suitability of egg hatching conditions and commonly available food plants for rearing the long-horned grasshopper Ruspolia differens Serville (Orthoptera: Tettigoniidae)

Efforts to promote sustainable production and processing of Ruspolia differens Serville (Orthoptera: Tettigoniidae) as a viable agribusiness model for enhancing food and nutrition security have gained momentum. However, the inexistence of rearing techniques adapted to this insect creates uncertainty regarding the effectiveness of up-scaling production. This study evaluated the effect of five temperatures (26, 28, 30, 32 and 34 °C) on egg development time, percentage hatchability and nymphal weight at hatching. It also evaluated the average weekly wet weight attained by R. differens and percentage survival during growth when reared at 30 °C on four different food plant diets. The diets composed of (1) star grass Cynodon dactylon (L.) Pers.; (2) wild millet Eleusine indica (L.) Gaertn.; (3) guinea grass Panicum maximum Jacq.; and (4) a mixture of the three food plants. The highest hatchability (89.33±3.06%) was observed for egg clusters that were not detached from the leaf sheaths and incubated at 30 °C. At the same temperature, the hatchability of eggs detached from the leaf sheath was 43.33±4.16%. The wet nymphal weight at hatching varied significantly across the different incubation temperatures. For eggs that were not detached from the leaf sheath, it ranged between 3.12±1.20 mg at 30 °C to 4.15±0.98 mg at 34 °C, while for eggs that were detached, it ranged between 2.96±1.14 at 32 °C to 6.0±2.0 mg at 26 °C. The highest wet nymphal weight (586.4 mg) and growth rate (10.47 mg/day) of adult R. differens after 8 weeks was recorded on wild millet, followed by the mixture of the three food plants (553.7 mg; 9.9 mg/day). Food plants significantly influenced survival of nymphs, with C. dactylon and P. maximum associated with the highest survival rate (53.3%). These findings are central to upscaling R. differens production.

A New Host Record and Rate of Parasitism for Trissolcus semistriatus (Hymenoptera: Scelionidae)

During a survey on insect egg parasitoids in Usak province (Turkey), parasitized egg clusters of Chlorochroa juniperina (L.) (Hemiptera: Pentatomidae) were collected on Juniperus oxycedrus L. (Cupressaceae). After emergence, the egg parasitoid was identified as Trissolcus semistriatus Nees (Hymenoptera: Scelionidae). This is the first record of this parasitoid reared from the egg masses of C. juniperina. This species has not been previously reported for T. semistriatus as a host species. Mainly eggs of Eurygaster spp. and different pentatomid species were used as hosts in mass culture of the parasitoid. Eggs of this species are acceptable as an alternative host to T. semistriatus during the summer. During 2016 and 2017, 61 egg clusters were collected for the first year and 83 egg clusters were collected for the second year. They have been determined to be parasitized by 31% and 27%, respectively, over the years. Also the rate of emergence and sex ratios were calculated as 98% and 79% in the egg clusters. According to these results, T. semistriatus has an important effect on the populations of C. juniperina under natural conditions in Usak province of Turkey.

New bioethological observations on Brahmaea (Acanthobrahmaea) europaea and its host plants in Special Area of Conservation “Grotticelle di Monticchio” (Basilicata, Southern Italy) (Lepidoptera: Brahmaeidae)

Brahmaea (Acanthobrahmaea) europaea Hartig, 1963, is an Italian endemic exhibiting an exceedingly restricted geographic distribution. In 1971, a protected site was established for the species: the Nature Reserve of “Grotticelle” (Basilicata Region). Then, the Reserve area was incorporated into the perimeter of the Special Area of Conservation “Grotticelle di Monticchio”. In 1997, for the first time, a group of B. (A.) europaea caterpillars was found in nature. During research conducted in 2013-2014, an egg cluster of B. europaea was observed for the first time, and other groups of larvae were found inside the Reserve. Additional information was acquired about mobility of the caterpillars during their development. Palatability tests allowed to attest Fraxinus angustifolia subsp. oxycarpa, Ligustrum vulgare and Phyllirea latifolia as food plants of the moth among those present in the Reserve. From spring 2015 to spring 2017 other bioethological observations on B. europaea were conducted, as well as surveys aimed to study the distribution of its host plants in the habitats of SAC “Grotticelle di Monticchio”. During 2016, ten egg clusters and numerous groups of caterpillars have been identified on 12 different trees. In 2017, an egg cluster was observed, and other groups of larvae were found. These finding allowed to observe other details on spawning and behaviour of the caterpillars, until to pupate. In addition, a map of local habitat 91B0 “Thermophilous Fraxinus angustifolia woods” is also presented.

Behavioural study of the golden apple snail (Pomacea canaliculata) in a Tropical Lake, Chenderoh Reservoir, Malaysia

AbstractA survey on the egg deposition behaviour of the golden apple snail (Pomacea canaliculata) was conducted at Chenderoh Reservoir in Malaysia. The distribution of P. canaliculata and medium preferences for egg deposition in the lake were recorded. The egg deposition mediums included aquatic plants, rocks and boats and other artificial structures. The number of egg clusters on the aquatic plants was counted to examine the preferred plant species for egg deposition, being collected thereafter for hatching test. This study findings indicated P. canaliculata laid eggs on the stems and leaves of aquatic plants, with a 43% occurrence compared to the other hard medium surfaces such as boats, rocks, fish cages and emerged bamboo piles, with a 14% occurrence recorded for each medium. A total of 65% of the eggs were deposited on the stems, and 35% on the leaves, of the aquatic plants. Phragmites australis (41%) of the Poaceae family was the most preferred plant for egg deposition, whereas the least preferred plant for egg deposition was Neptunia oleracea (3%) of the Fabaceae family. There was no significant difference (p < 0.5) in the percentage of hatched egg between the submersed and nonsubmersed hatching tests. The incubation period of the egg to hatch period was approximately 14 days upon the hardening of the calcium shell. In addition, about 60% of the eggs hatched, even though the eggs were immersed in the water. As the invasive P. canaliculata is considered to be in the top 100 of the “World Most Invasive Alien Species,” these types of behavioural studies are needed to better understand and control the snail, reducing the economic loss, especially in the agriculture sector, as well as facilitating a healthier lake environment.

Host-Acceptance Behavior of Trissolcus japonicus (Hymenoptera: Scelionidae) Reared on the Invasive Halyomorpha halys (Heteroptera: Pentatomidae) and Nontarget Species

Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is an egg parasitoid wasp from East Asia. It is considered to be an important natural enemy of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). Ongoing efforts to evaluate the physiological host range of this potential classical biological control agent have demonstrated that the wasp can parasitize at least 11 genera of nontarget Pentatomoidea in North America in no-choice tests. However, factors such as host-acceptance behavior that might affect nontarget parasitism in the field are poorly understood. We evaluated the preference of T. japonicus females provided with egg clusters of H. halys, Thyanta custator accerra McAtee (Hemiptera: Pentatomidae), Podisus maculiventris (Say) (Hemiptera: Pentatomidae), and Euschistus variolarius (Palisot de Beauvois) (Hemiptera: Pentatomidae) when wasps were reared on the target pest, H. halys, and the nontarget species, T.c. accerra and P. maculiventris. When reared on H. halys, T. japonicus showed a strong preference for H. halys, and frequently rejected nontarget hosts after inspection. When T. japonicus was reared on nontarget hosts, females showed reduced host-specificity, but were significantly smaller and produced a lower number of offspring. These results suggest that innate host-acceptance behavior is likely to reduce parasitism on some nontarget Pentatomoidea which T. japonicus will encounter in the field. Future efforts should be made to examine the ability of the wasp to reproduce long term on nontarget species when H. halys eggs are limited.

Nutrient Content of Brown Marmorated Stink Bug Eggs and Comparisons Between Experimental Uses

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), the brown marmorated stink bug (BMSB), has become a major pest. Seven experiments examined the nutrient content of their eggs in the context of female reproductive investment and use for experiments. Among 542 clusters examined, an average egg contained 23.50 ± 0.561 µg lipid, 3.17 ± 0.089 µg glycogen, and 3.08 ± 0.056 µg sugar. Mature eggs within a female’s ovary can make up 61% of her total lipid, 35% of glycogen, and 20% of sugar levels. Eggs obtained from a colony reared on a steady diet are expected to have consistent nutrient content. The age of a parental female only slightly affected the lipid level of oviposited eggs but did not affect glycogen or sugar levels. However, egg nutrient content can differ substantially by the source of the parental females; wild eggs had higher lipid but lower sugar content than colony-produced eggs. Further, the length of time that eggs are frozen influenced egg nutrient content. Freshly laid eggs had higher lipid and lower sugar levels than eggs frozen for 1 or 2 yr. Whether an egg turned grey following removal from cold storage did not affect nutrient content, nor did being frozen within 1 or 3 d of oviposition. The temperature at which eggs were left exposed did not impact egg nutrient content, but glycogen decreased and sugar increased with deployment time. This information combined with how factors affect host selection by natural enemies will help refine future experiments that use BMSB egg clusters.

Cuttlefish

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No nutritional benefits of egg cannibalism for Coleomegilla maculata (Coleoptera: Coccinellidae) on a high-quality diet.

Egg cannibalism serves various functions in the Coccinellidae. Here we examined the fitness consequences of egg cannibalism by neonates, fourth instar larvae, and prereproductive adults of Coleomegilla maculata DeGeer, with beetles fed a diet of Ephestia kuehniella Zeller eggs. Cannibalism of two eggs by neonates had no effect on development, and cannibalism of five eggs by fourth instars did not benefit any aspect of reproduction, but delayed pupation slightly. Cannibalism of eggs by pre-reproductive adults had no effect on reproductive success in any combination of reciprocal crosses of cannibals and non-cannibals. Females did not recognize, nor avoid consuming, their own clutches, and cannibalism propensity did not change following mating and onset of oviposition in either sex. These results contrast with those for more strictly aphidophagous species in which larvae gain developmental benefits, and females may recognize and avoid filial egg clusters while using cannibalism to interfere with conspecific females, whereas males reduce egg cannibalism after mating because they cannot recognize filial clusters. Egg cannibalism may confer developmental benefits to C. maculata when diet is suboptimal, as previously shown, but no such benefits were evident on the high-quality E. kuehniella egg diet. Female C. maculata do not require aphids to reproduce and distribute their eggs broadly in the environment, given that larvae can develop on pollen and non-aphid prey. Thus, C. maculata is not subject to the intraspecific competition that selects for cannibalism in more aphidophagous species, and also lacks many secondary adaptations associated with the behaviour.

Plant response to butterfly eggs: inducibility, severity and success of egg-killing leaf necrosis depends on plant genotype and egg clustering

Plants employ various defences killing the insect attacker in an early stage. Oviposition by cabbage white butterflies (Pieris spp.) on brassicaceous plants, including Brassica nigra, induces a hypersensitive response (HR) - like leaf necrosis promoting desiccation of eggs. To gain a deeper insight into the arms race between butterflies and plants, we conducted field and greenhouse experiments using different B. nigra genotypes. We investigated variation in HR and consequent survival of P. brassicae egg clusters. Impact of egg density, distribution type and humidity on HR formation and egg survival was tested. HR differed among plant genotypes as well as plant individuals. Egg density per plant did not affect HR formation. Remarkably, egg survival did not depend on the formation of HR, unless butterflies were forced to lay single eggs. Larval hatching success from single eggs was lower on plants expressing HR. This may be due to increased vulnerability of single eggs to low humidity conditions at necrotic leaf sites. We conclude that effectiveness of HR-like necrosis in B. nigra varies with plant genotype, plant individual and the type of egg laying behaviour (singly or clustered). By clustering eggs, cabbage white butterflies can escape the egg-killing, direct plant defence trait.

Oviposition preference and larval performance of sugarcane borer in eight sugarcane genotypes

ABSTRACT The sugarcane borer Diatraea saccharalis Fabr. (Lepidoptera: Crambidae) is one of the most important pests of sugarcane in the Americas. The purpose of this study was to assess multiple resistance traits in eight sugarcane genotypes against D. saccharalis, including five commercial cultivars and three exotic germplasm with potential to serve as resistance sources against this pest. The oviposition preference was assessed by using both free-choice and non-choice tests. The performance of both early stage larvae feeding on the leaves and late stages larvae feeding within the stalks were also assessed. There were differences among genotypes for number of both eggs and egg cluster in the free-choice test while no differences in non-choice test were observed. There were also differences in survival of early stage larvae feeding on the leaves, foliar injury rating and stalk damage. The genotype IM76-228 was the least preferred for oviposition and it seems that leaf width had some influence on adults’ preference rather than greening of the leaves. IM76-228 and RB867515 causes higher mortality of early stage larvae feeding in the stalks while IM76-228 and RB985523 had lower damage in both leaves and stalks. The genotype IM76-228 was the most resistant to D. saccharalis and could serve as genes sources for resistance in sugarcane breeding programs.

Larval food affects oviposition preference, female fecundity and offspring survival in Yponomeuta evonymellus

1. Yponomeuta evonymellus is a monophagous moth that feeds on Prunus padus which is native to Europe. In recent years, larval feeding and egg clusters have also been observed on non‐native Prunus serotina plants; however, survival of larvae on this new host is very low.2. The objective of the present study was to determine how the feeding of larvae on each of the two host plants impacts oviposition, offspring survival and fecundity in Y. evonymellus. Our hypothesis was that, under controlled conditions, females will lay eggs on the host on which they fed as larvae. We also hypothesised that the lower survival of young larvae feeding on P. serotina was due to the smaller buds and leaves present in this species, relative to those of P. padus.3. A dual‐choice experiment conducted under laboratory conditions demonstrated that females preferentially chose to oviposit on the plant species on which they fed as larvae. In the experiment, potential fecundity and offspring survival were significantly higher on P. padus than on P. serotina. The reduced performance of Y. evonymellus on P. serotina was correlated with a smaller bud mass and volume, lower leaf mass and surface area, and difficulty in constructing a protective tent against unfavourable weather conditions.4. In summary, the identity of the host plant species during larval feeding determines adult oviposition preference for that host species. The survival of larvae on P. serotina growing in the nature is low, but for phenology‐related reasons.

Oviposition Preference for Young Plants by the Large Cabbage Butterfly (Pieris brassicae) Does not Strongly Correlate with Caterpillar Performance

The effects of temporal variation in the quality of short-lived annual plants on oviposition preference and larval performance of insect herbivores has thus far received little attention. This study examines the effects of plant age on female oviposition preference and offspring performance in the large cabbage white butterfly Pieris brassicae. Adult female butterflies lay variable clusters of eggs on the underside of short-lived annual species in the family Brassicaceae, including the short-lived annuals Brassica nigra and Sinapis arvensis, which are important food plants for P. brassicae in The Netherlands. Here, we compared oviposition preference and larval performance of P. brassicae on three age classes (young, mature, and pre-senescing) of B. nigra and S. arvensis plants. Oviposition preference of P. brassicae declined with plant age in both plant species. Whereas larvae performed similarly on all three age classes in B. nigra, preference and performance were weakly correlated in S. arvensis. Analysis of primary (sugars and amino acids) and secondary (glucosinolates) chemistry in the plant shoots revealed that differences in their quality and quantity were more pronounced with respect to tissue type (leaves vs. flowers) than among different developmental stages of both plant species. Butterflies of P. brassicae may prefer younger and smaller plants for oviposition anticipating that future plant growth and size is optimally synchronized with the final larval instar, which contributes >80% of larval growth before pupation.

A microfluidic diode for sorting and immobilization of Caenorhabditis elegans.

Caenorhabditis elegans (C. elegans) is a powerful model organism extensively used in studies of human aging and diseases. Despite the numerous advantages of C. elegans as a model system, two biological characteristics may introduce complexity and variability to most studies: 1. it exhibits different biological features, composition and behaviors at different developmental stages; 2. it has very high mobility. Therefore, synchronization and immobilization of worm populations are often required. Conventionally, these processes are implemented through manual and chemical methods, which can be laborious, time-consuming and of low-throughput. Here we demonstrate a microfluidic design capable of simultaneously sorting worms by size at a throughput of 97±4 worms per minute, and allowing for worm collection or immobilization for further investigations. The key component, a microfluidic diode structure, comprises a curved head and a straight tail, which facilitates worms to enter from the curved end but prevents them from translocating from the straight side. This design remarkably enhances the efficiency and accuracy of worm sorting at relatively low flow rates, and hence provides a practical approach to sort worms even with the presence of egg clusters and debris. In addition, we show that well-sorted worms could be immobilized, kept alive and identically orientated, which could facilitate many C. elegans-based studies.

Oviposition Strategies of Florida Culex (Melanoconion) Mosquitoes.

In the genus Culex, oviposition is often generalized as laying floating egg rafts directly on the surface of the water, as reported for arbovirus vectors Culex pipiens L. and Culex tarsalis Coquillett, both members of subgenus Culex. The current work reports on investigations of exceptions to this strategy by species of Melanoconion, a diverse and mostly tropical subgenus of Culex, with many arbovirus vectors. Wild gravid females from Vero Beach, FL, were introduced into outdoor cages with open water, partially covered water, and emergent solid structures for oviposition. Three species, Culex cedecei Stone and Hair, Culex iolambdis Dyar, and Culex pilosus Dyar and Knab laid vast majorities (80-100%) of egg clusters attached to solid surfaces, although at different heights and angles, while Culex atratus Theobald laid floating egg clusters (100%) directly on the water. When offered mud, open water, and woody material, Cx. iolambdis laid 86% of clusters on nearly vertical surfaces of mangrove rootlets. Culex iolambdis eggs laid on solid surfaces hatched within 3-4 d or dried up without hatching. Results suggest that Melanoconion species utilize a variety of oviposition strategies, yet most species studied oviposit out of water. For some species, such as Cx. pilosus, this is a strategy for diapause and desiccation resistance, while for others, such as Cx. iolambdis, ovipositing above water may protect eggs from predators or being flushed from larval habitat. A summary of oviposition strategies in genus Culex shows that above-water oviposition is widespread and that the Culex egg raft paradigm needs reassessment.

Non-parasitic life cycle of the cattle tick Rhipicephalus (Boophilus) microplus in Panicum maximum pastures in northern Argentina

The aim of this work was to study the non-parasitic phase of the Rhipicephalus microplus life cycle in Panicum maximum grasses from northern Argentina, in order to provide ecological information for designing methods of tick control. Four localities were chosen as replicates. The biological parameters measured were proportion of females ovipositing, the pre-oviposition period, the proportion of egg clusters hatching, the incubation period of eggs, larval longevity, and the total non-parasitic period (time from the exposure of the female to the date of death of the last larva) (TNPP)). The following general trends were observed: I) a longer TNPP occurred when female ticks were exposed in mid- and late summer and early spring; II) the shortest TNPP occurred when female ticks were exposed from late winter to late spring; III) larvae that were active in early and mid-summer had the shortest longevity; IV) incubation periods of eggs, which originated from females exposed in late summer, early autumn and mid-spring, were longer than the incubation period of eggs produced by females exposed in late spring and early summer; V) eggs did not hatch when the engorged females were exposed in the pastures in mid- and late autumn and winter. The spelling period of the P. maximum grasses that is needed to ensure total control of R. microplus consists of 19–20weeks if the spelling starts in late spring and early summer, and 27–28weeks if the spelling begins in mid- and late summer or in autumn.

Life history of Paraselenis (Spaethiechoma) dichroa (Germar, 1824) (Coleoptera: Chrysomelidae: Cassidinae) in natural conditions of Atlantic Forest from Brazil

ABSTRACTCassidinae Gyllenhaal​ is the second largest subfamily of Chrysomelidae (Coleoptera), which presents characteristic morphology, biology and behaviour. The current study describes the life cycle of Paraselenis(Spaetiechoma) dichroa (Germar), ​determining biological and behavioural aspects as well as the action of natural enemies on populations, when the species has maternal care. The study was conducted between February and April 2015 in the National Forest of Passa Quatro, municipality of Passa Quatro, Minas Gerais state, Brazil. Daily observations were made (morning and afternoon) to evaluate the offspring of females on Ipomoea sp. and Merremia macrocalyx (O’Donell​) (Convolvulaceae), as well as the actions of natural enemies on the young. The eggs are deposited on the midrib and abaxial surface of leaves (n = 25). Egg clusters are pedunculated, arranged in groups and devoid of any cover. On average, each female produced 27.3 ± 5.6 (n = 16) eggs, with a mean incubation period of 12.7 ± 2.9 days (n = 10 females with their young). The larvae remained grouped in the leaves throughout development, except when they fed. They retained faeces and exuviae as a stacked faecal structure on their mobile urogomphi (caudal process) like a faecal shield. The mean number of larvae per female was 12.7 ± 10.1 (n = 19) and the larval period lasted 24.9 ± 4.5 days (n = 12). Pupation occurred on the stem of the plant (n = 16). On average there were 8.1 ± 8.5 individuals for pupae progeny (n = 14). The mean duration of the pupal stage was 10.4 ± 3.3 days (n = 5). Overall, 3% of adults emerged (n = 13 individuals), with a total cycle time of 41.3 ± 8.4 days (n = 6). Adults are sexually dimorphic in the elytral shape. Females remain with the offspring throughout development. The natural enemies of immatures were Emersonella pubipennis Hansson​ (Hymenoptera: Eulophidae), Tachinidae (Diptera) and Stiretrus decastigmus (Herrich-Schaeffer​) (Heteroptera: Pentatomidae), Conura sp. Spinola​ (Hymenoptera: Chalcididae) and Brachymeria sp. Westwood​ (Hymenoptera: Chalcididae). The information presented here on the natural history of P. dichroa are important as they may serve as a starting point to understand evolutionary questions and multispecies interactions.

Biology and Food Habits of the Invasive SnailAllopeas gracile(Gastropoda: Subulinidae)

The biology of the widely occurring but poorly known terrestrial snail Allopeas gracile (Hutton, 1834) (Gastropoda: Subulinidae) was determined, emphasizing food relationships. Isolated snails reproduced without cross fertilization. These snails deposited small clusters of eggs (3–7 per d) totaling about 20 per mo once oviposition commenced (after about 50 d). The snails grew rapidly for 50 d, attaining a mass of about 25 mg, then grew more slowly, eventually attaining a mass of about 50 mg after 250 d. Hatching occurred over a wide range of temperatures. The mean duration of the egg stage decreased from 18.7 to 8.0 d as the temperature increased from 19.5 to 32.0 °C. Allopeas gracile was omnivorous, feeding on green plants (vegetables, weeds, and flowers), fungi (cultivated mushroom and sooty mold), and animal matter (dead cockroaches and earthworms), but not decaying vegetation (tree leaves). Although this species is omnivorous, many plants allowed only maintenance, not fostering rapid growth. These small snails consumed only about 1.5 cm2 per d of favored food (lettuce) at maturity, and considerably less of most plants offered. This invasive snail does not seem to be destined to be a significant pest except perhaps under restricted circumstances.

Distribution in the abundance and biomass of shelled pteropods in surface waters of the Indian sector of the Antarctic Ocean in mid-summer

We investigated shelled pteropod abundance and biomass with a 100-μm closing net, and their estimated downward fluxes using a sediment trap installed in a drifter buoy in the Indian sector of the Antarctic Ocean during the austral summer. Over 90% pteropod abundance was distributed in the upper 50 m; 70–100% were immature veligers. Limacina retroversa was dominant in the >0.2 mm individuals north of 60°S, L. helicina dominated south of 62°S, while populations around 60–62°S were mixed. Unidentifiable small Limacina spp. (ssL) were highly abundant in the upper 50 m at 60°S, 63°S, and 64°S on 110°E and 63°S on 115°E, although their estimated particulate organic carbon (POC) biomasses were less than that of Limacina adults. Adult females bearing egg clusters were found in the 0–50 m layer; the veligers likely grew within a short period. The mean downward flux of ssL and veligers at 70 m around 60°S, 110°E was 5.1 ± 1.6 × 103 ind. m−2 d−1 (0.6 ± 0.2 mg C m−2 d−1), which was 3.8% of the integrated ssL and veligers in the upper 70 m, suggesting that at least 4% of the veligers were produced daily in the surface layers. The mid-summer spawned ssL and veligers likely contributed to the subsequent increase in large pteropods in the area.

Patogenitas cendawan entomopatogen Nomuraea rileyi (Farl.) Sams. terhadap hama Spodoptera exigua Hübner (Lepidoptera: Noctuidae)

The purpose of this research is to study the pathogenicity of Nomuraea rileyi (Farl.) Sams. to eggs and larvae of Spodoptera exigua Hübner (Lepidoptera: Noctuidae).The fungi were isolated from insect cadaver of S. exigua. Egg clusters and several instar larvae with different conidial concentrations (106 – 109 conidia/ml) were used in the experiment. The results of experiment showed that there was no effect of all concentrations of fungi on egg mortality. Mortality of S. exigua larvae was dependent on the instar and conidial concentration. Generally with increasing conidial concentrations, the mortality were also increasing.

Random pattern of parasitism and female-biased sex ratio in the egg parasitoid Neochrysocharis formosa attacking the pine sawfly Diprion pini in mountain forests of Spain

The most harmful hymenopteran pests of Pinus sylvestris L. are conifer sawflies from the family Diprionidae, including the widespread Diprion pini (L.). Natural enemies of this pest are still poorly known in many European areas where attacks occur. We studied the egg parasitoids of D. pini at four sites in two mountainous areas of Spain: the Sierra de Francia (western Spain) and the Sierra de Albarracin (eastern Spain). At all sites, the dominant egg parasitoid was Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae), whereas other three chalcidoid species were rare. All these species were previously recorded in association with D. pini, but we report here their first record in Spain. Neochrysocharis formosa attacked up to 32.3% of egg clusters of D. pini in the Sierra de Albarracin and 18.5% in the Sierra de Francia. In the attacked egg clusters, this species parasitized up to 35% of eggs in the Sierra de Albarracin and 23.7% in the Sierra de Francia, with a marked female-biased sex ratio. Contrary to the clustered pattern of parasitism observed for N. formosa while attacking other gregarious diprionids, the oviposition in egg clusters of D. pini followed a random pattern, probably due to the froth roof (spumous coating) that covers its eggs and interferes with the egg-searching behavior of females. Indeed, other parasitoid species of D. pini have been reported to behave similarly.