Survival Of First-instar Larvae Research Articles

How the seed coat affects the mother\u2019s oviposition preference and larval performance in the bean beetle (Acanthoscelides obtectus, Coleoptera: Chrysomelidae, Bruchinae) in leguminous species

BackgroundThe host specificity and host range of the dry bean beetle, Acanthoscelides obtectus (Coleoptera: Chrysomelidae, Bruchinae), a seed predator of beans, is poorly known. In addition, the female oviposition preference and larval performance relationship is complicated by the respective importance of seed coat and cotyledon, because, paradoxically, females lay eggs on the basis of stimuli of the seed coat alone, without directly being able to assess the quality of the cotyledon’s suitability for larval development. Conversely, the thickness of seed coat may prevent first instar larvae from entering the seeds, even if cotyledons are suitable for development.MethodsThe seeds of 62 leguminous species and 75 cultivars and accessions occurring in Hungary were evaluated for preference-performance relations. The preference of female bean beetles for seeds was measured in no-choice egg-laying tests. The ability of first instar larvae to overcome the seed coat as a physical barrier was tested with intact seed coat, while pre-drilled seed coats allowed the larvae to assess the suitability of cotyledon for development. The number of emerging adults was recorded. The thickness of seed coats and the weight of seeds were measured. Nonparametric tests and logistic regression were used for the statistical analyses of data and effect sizes were also calculated.ResultsSeeds of 18 leguminous species (35% of them Lathyrus) supported larval development to adults if the seed coat was pre-drilled; however, only nine leguminous species supported development to adults if the seed coat was intact. Seed coat thickness beyond a critical threshold of 0.1 mm strongly influenced survival of first instar larvae. There was no overall positive correlation between oviposition preference and larval performance, except for 16 so-called acceptable non-hosts (Kendall’s τ = 0.3088). A. obtectus females also showed an ovipositional hierarchy of legume species even in no-choice tests.ConclusionsThe results suggest that whereas the use of some acceptable non-host species by the A. obtectus is possible in seed stores, the same is unlikely under outdoor conditions, where the recognition of a diverse set of seed pod-related compounds would be necessary to induce egg-laying.

Insecticidal activities of garlic substances against adults of grain moth, Sitotroga cerealella (Lepidoptera: Gelechiidae)

Abstract The angoumois grain moth, Sitotroga cerealella (Olivier), is one of the most serious stored grain pests around the world. In attempts to reduce the losses caused by the moth and to suppress its populations, the fumigant activities, behavioral influence and ovipositional inhibition of garlic (Allium sativum) essential oil and its two major components, diallyl disulfide and diallyl trisulfide, were investigated against the adult grain moth. Their effects on reduction in survival of first instar larvae to adult emergence were also evaluated. Results showed that these three materials (garlic essential oil, diallyl disulfide and diallyl trisulfide) had significant fumigant activity with 50% lethal concentration values at 1.33, 0.99, and 1.02 μL/L air space, respectively; meanwhile, the three materials possessed high behavioral deterrent activities against adults in the Y‐tube olfactometer. When applied to rice grains, these materials reduced adult longevity and inhibited oviposition, with ovipositional inhibition above 70% at a concentration of 1.5 μL/25 g in either no‐choice or two‐choice tests. In short, the study showed that both diallyl disulfide and diallyl trisulfide, like garlic essential oil, acted as fumigants, produced behavioral deterrence and inhibited oviposition against angoumois grain moth. Our work here indicates that diallyl disulfide and diallyl trisulfide may serve as potential alternatives for grain protectants since both of them can be prepared easily from readily available chemicals.

Environmental risk assessment of veterinary pharmaceuticals: Development of a standard laboratory test with the dung beetle Aphodius constans

The environmental risk assessment of veterinary pharmaceuticals for dung beetles is required if the substance is an anti-parasiticide for the treatment of pasture animals. However, the demonstration of the environmental safety of those substances for dung fauna is hampered by the fact that no standardized laboratory test system is currently available. Here a test system using the temperate dung beetle species Aphodius (Agrilinus) constans (Scarabaeidae: Aphodiinae) Duftschmidt is described. The survival of first instar larvae of A. constans exposed to a model substance, dimethoate, spiked into formulated (i.e. dried, formulated and re-wetted) or fresh dung was measured over a period of three weeks. Larvae performed better in formulated dung which also proved to be more suitable for mixing-in test substances homogenously. Dimethoate caused significant larval mortality with LC50 values within a range of 1.3–2.8 mg a.s./kg dung (d.w.), depending on the dung type. Based on the data presented here, it is recommended to incorporate this new test system in the risk assessment process for veterinary pharmaceuticals. However, an international ringtest should to be performed beforehand to ensure adequate validation of the method.

New screening test to predict the potential impact of ivermectin-contaminated cattle dung on dung beetles

According to European Union recommendations, a test method has been developed to evaluate the effects of veterinary pharmaceuticals on dung feeding insects. This test method was evaluated with the dung beetle Aphodius constans by using fecal residues of ivermectin after a pour-on administration. Dung of different age (and thus containing different concentrations of ivermectin) as well as mixtures of highly-contaminated spiked dung with untreated control dung were studied in five test runs in two laboratories. The concentration of ivermectin (active substance; a.s.) in the dung samples was verified analytically. The main test endpoint was the survival of first instar larvae. The LC50 using dung directly obtained from treated cattle ranged from 470 to 692 microg a.s. kg(-1) dung (dry weight; d.w.) and 67 to 97 microg a.s. kg(-1) dung (fresh weight; f.w.). Using mixtures, the outcome of two tests was almost identical: 770 to 781 microg a.s. kg(-1) dung (d.w.); 109 to 132 microg a.s. kg(-1) dung (f.w.). In comparison to the LC50 values obtained when ivermectin was spiked in control dung at several concentrations (LC50 880-985 microg a.s. kg(-1) dung (d.w.)), the LC50 values were again very similar. Three conclusions can be drawn from these results. The proposed test method seems to be robust and allows for the initiation of an international validation process (including ringtesting). Because of only small differences found in tests in which the test substance was spiked into control dung and those in which dung from treated cattle was applied, the use of a standard test method is proposed. The effects of ivermectin on ecologically relevant dung beetles obtained in a standardised test method reflect the results from field studies and are in the range of environmentally relevant concentrations.

Toxic and Genotoxic Effects of Azaarenes: Isomers and Metabolites

Heterocyclic PAH and their metabolites can show toxic, mutagenic, carcinogenic and teratogenic effects. In this study, a relation between toxic and mutagenic effects, and chemical structures of nitrogen substituted polycyclic hetero-aromatic hydrocarbons was sought using seven azaarenes and two azaarene metabolites. Survival of first instar larvae of the midge Chironomus riparius was determined to measure toxicity. Mortality increased with increasing number of aromatic rings of the compound, but metabolism of acridine and phenanthridine to 9(10H)-acridone and 6(5H)-phenanthridinone. respectively, strongly decreased toxicity. However, acridone was the most genotoxic of the azaarenes tested in the MutatoxTM test. Although mortality and genotoxic activity are well described by molecular descriptors relevant to bioaccumulation, in both cases exceptions are found on this general rule, even between isomers. Furthermore, it is shown that metabolism of azaarenes changed the impact on different biological end-points, clearly putting severe limitations on environmental standards solely based on the narcotic effects of parent PAH.

Prediction of Resistance in Sugarcane to Stalk Borer Eldana saccharina by Near-Infrared Spectroscopy on Crude Budscale Extracts: Involvement of Chlorogenates and Flavonoids

Predictive models based on data acquired by near infrared (NIR) spectrophotometry suggest that components in extracts from sugarcane nodal budscales contribute towards resistance to the stalk borer Eldana saccharina. NIR spectra for 60 sugarcane clones varying in resistance to E. saccharina indicated that chlorogenates and flavonoids might be involved in the NIR calibration and also in the interaction between the insect and sugarcane. Two extreme types of flavonoid profile subsequently were revealed, one associated with resistance and the other with susceptibility. Incorporation of the susceptible type profile into a defined synthetic diet increased feeding initiation and subsequent survival of first instar larvae compared with the resistant type profile. NIR calibrations proved capable of predicting the resistance ratings of validation sets.

Viability of green lacewing Chrysoperla carnea Steph. (Neuropt., Chrysopidae) eggs stored in potential spray media, and subsequent effects on survival of first instar larvae

Abstract: At 4°C, green lacewing, Chrysoperla carnea eggs can be stored for one day in 0.125%; agar solution or in water without any reduction in hatch rate or larval survival compared with eggs kept in air. For eggs kept in solution for two or more days, hatch rate was clearly reduced, but those larvae that emerged survived as long as those emerging from eggs stored in air. No larvae emerged from eggs stored in solution for 8 days.

Survival of first instar larvae ofDanaus plexippus (Lepidoptera: Danainae) in relation to cardiac glycoside and latex content ofAsclepias humistrata (Asclepiadaceae)

Our paper addresses field survivorship of first instar monarch butterfly larvae (Danaus plexippus L., Lep.: Danainae) in relation to the dual cardenolide and latex chemical defenses of the sand hill milkweed plant,Asclepias humistrata (Asclepiadaceae) growing naturally in north central Florida. Survival of first instar larvae in the field was 11.5% in the first experiment (15–20 April 1990), and dropped to 3.4% in the second experiment (20–30 April). About 30% of the larvae were found glued to the leaf surface by the milkweed latex. Predator exclusion of non-flying inverte-brates by applying “tanglefoot” to the plant stems suggested that the balance of the mortality was due to volant inverte-brates, or to falling and/or moving off the plants. Regression analyses to isolate some of the other variables affecting survivorship indicated that first instar mortality was correlated with (1) increasing cardiac glycoside concentration of the leaves, (2) increasing age of the plants, and (3) the temporal increase in concentration of cardiac glycosides in the leaves. The study also provided confirmatory data of previous studies that wild monarch females tend to oviposit onA. humistrata plants containing intermediate concentrations of cardiac glycosides. Cardiac glycoside concentration in the leaves was not correlated with that in the latex. The concentration of cardenolide in the latex is extremely high, constituting an average of 1.2 and 9.5% of the mass of the wet and dry latex, respectively. The data suggest that an increase in water content of the latex is compensated for by an influx of cardenolide with the result that the cardenolide concentration remains constant in the latex systems of plants that are growing naturally. We also observed first instar larvae taking their first bite of milkweed leaves in the field. In addition to confirming other workers findings that monarch larvae possess elaborate “sabotaging” behaviour of the milkweed's latex system, we discovered that several larvae on their first bite involuntarily imbided a small globule of latex and instantly became cataleptic. This catalepsis, lasting up to 10 min, may have been in response to the high concentration of cardenolide present in the latex ofA. humistrata, more than 10 times that in the leaves. The results of the present study suggest that more attention should be directed to plant chemical defenses upon initial attack by first instar insect larvae, rather than attempting correlations of plant chemistry with older larvae that have already passed the early instar gauntlet. The first bite of neonate insects may be the most critical moment for coping with the chemical defenses of many plants and may play a much more important role in the evolution of insect herbivory than has previously been recognized.

Oviposition by Danaus plexippus in relation to cardenolide content of three Asclepias species in the southeastern U.S.A.

Abstract. 1. Female monarchs were observed in the field ovipositing on a native North American milkweek host, Asclepias humistrata L. As in a comparable Australian study on an introduced novel host (Asclepias fruticosa L.) we found post‐alighting rejection of plants with low and high cardiac glycoside concentration (CG).2. Most oviposition took place on plants with CG in the range 200–500 μg/0.1 g dry weight. Thin‐layer chromatography showed no obvious qualitative difference in cardenolide types between accepted and rejected plants, excepting an indication that rejected plants may have a higher level of more polar cardenolides.3. In a controlled laboratory experiment comparing oviposition on a low (A.incarnata L.) vs high (A.curassavica L.) CG host plant species we found no relationship between CG and oviposition on the low CG species, but a negative relationship in the high CG species. This corroborates our findings on oviposition on single host species in the field.4. We also record the first indication of a physiological cost of monarch larvae feeding on plants high in CG. There was a significant negative relationship between survival of first instar larvae and CG levels in plants. This study opens the way for further work on the association of monarch butterflies and their toxic milkweed hosts.

LABORATORY STUDIES ON DEVELOPMENT OF GYPSY MOTH, LYMANTRIA DISPAR (L.) (LEPIDOPTERA: LYMANTRIIDAE), LARVAE ON FOLIAGE OF GYMNOSPERMS

AbstractThe development of gypsy moth larvae was monitored in the laboratory on the foliage of 39 species belonging to 18 genera in the Araucaraceae, Cupressaceae, Ginkgoaceae, Pinaceae, Taxaceae, and Taxodiaceae. Larval survival through successive molts, time of larval development, live female pupal weights, and adult female production of ova were measured as indicators of host plant suitability for the gypsy moth. The criteria for distinguishing the most suitable hosts were as follows: (1) greater than 80% survival of first-instar larvae, (2) development to pupation in less than 41 days, (3) female pupal weights over 1099 mg, and (4) the production of more than 350 ova. The most suitable species were in the Pinaceae, in particular, Cedrus deodara (Roxb. ex Lamb.) G. Don, Larix decidua Mill., and Picea pungens Engelm. The least suitable species were in the Cupressaceae, Ginkgoaceae, and Taxaceae. First-, second-, and third-instar larvae often differed in their ability to survive on new foliage compared with foliage from the previous year. Overall, first-instar larvae successfully developed into adults on 20 of the species tested but second-instar larvae developed into adults on 29 of the species tested. First- through fourth- or fifth-instar larvae failed to develop into adults on eight of the species tested.

Impact of differential feeding on the reproduction of tiger beetleCicindela cancellata DeJean (Cicindelidae: Coleoptera)

Tiger beetles belonging to the family Cicindelidae are exclusively predaceous and have great impact on the natural eco-balance. Recent studies have revealed the existence of more than 300 species all over India under divergent habitats and none have been exploited for biological control of insect pests. Studies on the impact of differential feeding on the reproduction ofCicindella cancellata revealed a definite relationship between the quality and quantity of food consumed by adults on the fecundity, egg size, longevity of the adults, larval emergence pattern and the survivability of first instar larvae.Corcyra cephalonica larvae fed 3 times a day (55·74 mg) resulted in maximum egg production, longer adult life and longer survival of first instar larvae, followed by Corcyra, one larvae per day (37·16 mg) and mixed food of spiders, hoppers and Corcyra (alternately) 32·81 mg). Least fecundity was observed when fed with ants alone and no eggs with no food.

SURVIVAL OF FIRST INSTAR LARVAE OF PTEROHELAEUS DARLINGENSIS CARTER (COLEOPTERA: TENEBRIONIDAE) EXPOSED TO HIGH TEMPERATURES: A LABORATORY STUDY

ABSTRACTFirst instar larvae of Pterohelaeus darlingensis were exposed for up to 5 periods of up to 48 h to temperatures between 29–45°C in soils of 10 or 30% soil moisture to define empirically the effects of these parameters on survival. In general, survival was greater in moist soil than in dry soil. Survival decreased exponentially with increasing exposure. Repeated exposures to sublethal temperatures in moist soil caused higher mortality than at previous exposures to the same temperature. The reverse relationship held for exposures in dry soil. These results are used to develop a mathematical model of survival of first instar larvae which should allow prediction of survival in the field.

Effects of High Temperature and Soil Moisture on Survival of First-Instar Larvae of the Scarab Anoplognathus porosus (Dalman) (Coleoptera)

On the pastorally rich New England Tablelands (north-eastern New South Wales in Australia), there are over twenty-five pasture scarab species, many occurring together throughout the area (R. J. Roberts, personal communication). Sometimes these insects become so numerous that serious damage to pasture results. No control or management procedure yet proposed has prevented this damage. In summer the scarab larvae, which aggregate near the surface of the soil, are subjected to short exposures to temperatures above 30° C. These temperatures have proved to be lethal to some larvae of Sericesthis nigrolineata Boisduval (Davidson, Wiseman & Wolfe 1972a, b). Using laboratory data on survival at high temperatures and various soil moistures, Davidson, Wiseman & Wolfe (1970) predicted the level of survival of larval populations in field experimental plots near Armidale. A similar investigation with larvae of Anoplognathus porosus (Dalman) is described in this paper.

The sensitivity of scale insects to 14 C -particles and to 60 CO gamma rays.

SummaryThe concentrations of 14C which can be tolerated by the scale insect Aonidiella aurantii (Mask) throughout its development have been investigated.Dose-survival curves show the activity of 14C in insects in relation to the survival of first instar larvae, the emergence of winged males and the reproduction of females. The 50 per cent survival values, in terms of the concentrations of 14C in the insects at these stages, were about 680 µCi gm−1, 360 µCi gm−1 and 24 µCi gm−1, respectively. Calculations of the equivalent dose-rates from β-particles are attempted.The sensitivity to 60Co γ-rays of insects of various ages was studied. Dose-survival curves show that irradiation prior to moulting is about three times as effective as irradiation during moulting, and that irradiation at an early age has an effect on later development. These findings were used in calculating the cumulative doses from 14C.At the 50 per cent survival level, the cumulative dose from 14C, adjusted for changes in sensitivity with time, was estimated to be about 7600 rads for first instar larvae, 9800 rads for emerging males and 4200 rads for reproduction in females. These values are about three times the minimum γ-ray doses which produced similar effects.

Survival of crawlers of California red scale, Aonidiella aurantoo (Mask.) (Homoptera : Diaspididae)

The periods of survival of first-instar larvae (crawlers) of California red scale were estimated in the laboratory under conditions that attempted to simulate those that the crawlers would be exposed to during dispersal by wind in the field. Since attempts to keep crawlers suspended in a stream of moving air for long periods were unsuccessful, they were placed in small cages, and air at constant temperature and humidity was passed through the cages at known rates. Following exposure, the crawlers were transferred to lemon leaf discs, and only those able to begin feeding and secrete a scale were recorded as survivors. At 15�C crawlers survived a mean period of 17.1 hr at 70% R.H. and 14.2 hr at 35% R.H.; at 2S�C, 10.1 hr at 70% R.H. and 6.8 hr at 25% R.H.; at 3SCC, 7.2 hr at 70% R.H. and 5.7 hr at 25% R.H. The period survived was significantly higher at the higher humidity in each case. At 70% R.H. the period of survival decreased significantly with increased temperature. At 25% R.H. the period was significantly higher at 15�C than at 2S�C, but not between 25 and 35�C. The period of survival decreased as the rate of flow of air past the crawlers increased to the terminal velocity. The long periods of survival of crawlers, even under extreme conditions to which they would rarely be exposed in nature because of their rhythm of emergence, leaves little doubt that they could withstand transport by wind over long distances even during hot, dry summer weather.

Environmental Stress in the Pasture Scarab Sericesthis nigrolineata Boisd. II. Effects of Soil Moisture and Temperature on Survival of First-Instar Larvae

The larvae of the melolonthine, ruteline and dynastine scarabs of the Northern Tablelands region of New South Wales remain underground throughout their three larval instars and during metamorphosis to adults. The eggs of these species are laid mainly in December and January, and first-instar larvae occur from January to April. At this time of year extremes of wet and dry may be experienced on the Tablelands, since evaporation is high (mean monthly evaporation 150 mm), and the rainfall very variable about the monthly mean of 80 mm at Armidale. Soil moistures are frequently below permanent wilting point between December and April (Begg 1959), yet in some years the soils on the Tablelands are saturated for prolonged periods. An example of this variability was seen in 1971 when rainfall near Armidale was 106 mm and evaporation was 106 mm during February, while in March of the same year rainfall was only 4 mm and evaporation was 123 mm. Field studies have shown that about 60% of first-instar larvae of local scarab species occur in the upper 5 cm of soils under pasture, a depth at which soil moisture and temperature fluctuate widely. In the first paper in this series the mortality caused by exposure of larvae of Sericesthis nigrolineata Boisd. to high temperatures in soils above wilting point and below field capacity was discussed (Davidson, Wiseman & Wolfe 1972). The present paper deals with laboratory studies of survival of first-instar larvae in wet and dry soil at various temperatures. The aim of the work is to provide empirical data from which mortality in the field can be predicted.

The Congo Floor Maggot,Auchmeromyia luteola(F.), in a Laboratory Culture

The Congo Floor Maggot,<i>Auchmeromyia luteola</i>(F.), in a Laboratory Culture