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1.
Myron P. Zalucki Stephen B. Malcolm Christopher C. Hanlon Timothy D. Paine 《Chemoecology》2012,22(2):75-88
Growth rate and survival of first-instar larvae of Danaus plexippus, a milkweed specialist, depended on milkweed species, and was related to the amount of latex produced from wounds, leaf cardenolide
concentrations and the presence of leaf hairs. Larval growth was more rapid and survival was higher on leaves of Asclepias californica with experimentally reduced latex, and this species has characteristically high latex, low- to mid-range cardenolide concentrations,
and very hirsute leaves. Similarly, growth was higher on reduced latex leaves of both A. eriocarpa (a high latex/high cardenolide, hirsute species) and A. erosa (glabrous fleshy leaves, high latex/high cardenolides). There were no differences in either survival or growth rate between
larvae on reduced latex or control leaves of the low latex/low cardenolide A. fascicularis with soft glabrous leaves and both survival and growth rate were higher on this species than the other species tested. Larval
growth rates on leaves with reduced latex were similar among ten milkweed species tested to date but differed from growth
rates on intact leaves suggesting that latex and possibly included cardenolides are both important in first-instar monarch
larval growth, development and survival. We show for a range of ecologically important milkweeds that experiments on cut plant
material (no latex outflow) lead to higher growth rates compared to intact plants. Such laboratory assays based on detached
leaves will be misleading if the objective is to determine the impact of treatments such as Bt-maize pollen on monarchs on field plants. 相似文献
2.
Summary. Late instar larvae of the monarch butterfly (Danaus plexippus L., Lepidoptera: Nymphalidae) deactivate the latex defense of milkweeds by chewing a furrow in the leaf midrib or petiole. The larva then feeds beyond the cut where latex outflow is minimal. If a larva does encounter latex exudate during feeding, it often returns to its initial cut to damage the midrib or petiole more extensively before resuming feeding. We used this response to latex as an assay for testing what cue triggers vein cutting. A sticky solution of polyethylene glycol and a mixture of cardenolides both were ineffective; drops applied to the mouthparts of feeding monarchs failed to elicit renewed vein cutting. Activity resided instead within a methanol extract of the supernatant obtained from centrifuged latex of the milkweed, Asclepias curassavica L. (Asclepiadaceae). Treatment with proteinase K did not eliminate activity documenting that the active compound is unlikely to be proteinaceous. Our results indicate that latex adhesiveness and low polarity cardenolides are relatively unimportant releasers of vein cutting. We propose that milkweeds contain noncardenolide stimulants of vein cutting; these compounds presumably serve a defensive role for milkweeds. Over 50 species of insects are known to employ vein-cutting before feeding on plants with canal-borne exudates; most of these species are dietary specialists like the monarch. Our behavioral assay provides a novel approach for identifying ecologically-significant compounds in the exudates of their diverse host plants. 相似文献
3.
Stephen B. Malcolm 《Chemoecology》1990,1(1):12-21
Summary Cardenolide sequestration by a hemimetabolous aphid and a holometabolous butterfly from the neotropical milkweed,Asclepias curassavica L., is compared. The oleander aphid,Aphis nerii B. de F., sequestered a similarly narrow range of cardenolide concentrations to the monarch butterfly,Danaus plexippus (L.), from the wide range of concentrations available in leaves of A.curassavica. However, A.nerii sequestered significantly less cardenolide (269 µg/0.1 g) thanD. plexippus (528 µg/0.1 g). The honeydew excreted by A.nerii was comprised of 46% cardenolide. The complete polarity range of 25 cardenolides detected by thin layer chromatography in A.curassavica was represented in the 17 whole aphid cardenolides and the 20 aphid honeydew cardenolides detected. D.plexippus sequestered a narrower polarity range of 11 cardenolides, having eliminated low polarity cardenolide genins and glycosides. It is suggested that these chemical differences may be related to interactions among the broad feeding tactics of sucking or chewing milkweed leaves, life history constraints of holometabolyversus hemimetaboly, the distribution of milkweed food resources in space and time, and the dynamics of natural enemies. 相似文献
4.
Summary 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. 相似文献
5.
Letizia Mattiacci Sara Rudelli Bettina Ambühl Rocca Sem Genini Silvia Dorn 《Chemoecology》2001,11(4):167-173
Summary. Plant responses to herbivory might directly affect the herbivore (“direct” defences) or might benefit the plant by promoting
the effectiveness of natural antagonists of the herbivores (“indirect” defences). Brussels sprouts attacked by Pieris brassicae larvae release volatiles that attract a natural antagonist of the herbivores, the parasitoid Cotesia glomerata, to the damaged plant. In a previous study, we observed that feeding by caterpillars on the lower leaves of the plant triggers
the systemic release of volatiles detectable by the parasitoids from upper leaves of the same plant.?The role of these systemically
induced volatiles as indirect defence and the dynamics of their emission were investigated in wind-tunnel dual choice tests
with C. glomerata. The systemically induced emission of volatiles varied depending on leaf age and on plant age. Systemic induction affected
parasitoid effectiveness, as induced plants could be more easily located by parasitoids than non-induced ones.?The role of
the systemic induction as a direct defence was investigated through behavioural and feeding tests with P. brassicae. In dual choice assays, 1st instar larvae preferred to feed and fed more on systemically induced than on non-induced leaves.
In single choice assays, the leaf area consumed by caterpillars was larger on systemically induced leaves than on non-induced
control leaves. However, caterpillars fed on systemically induced leaves attained the same weight as those feeding on non-induced
controls. In addition, P. brassicae pupae whose larvae were fed on systemically induced leaves had longer developmental times than those of larvae fed on non-induced
leaves. Adult oviposition behavior was not influenced by systemic induction.?We conclude that systemically induced responses
in cabbage might reduce P. brassicae fitness both directly, by affecting their development and feeding behavior and indirectly by making caterpillars and pupae
more vulnerable to attack by carnivores. The occurrence of a possible relationship between direct and indirect defence is
discussed.
Received 24 January 2001; accepted 3 May 2001. 相似文献
6.
Summary. Leaf disc choice and oviposition bioassays were used to examine the effects of larval experience with a Hoodia gordonii latex on subsequent behaviors. The latex deterred feeding and oviposition by “naïve” cabbage looper (Trichoplusia ni, Noctuidae) larvae and moths with no previous exposure to the material. “Experienced” insects, reared on a diet with the H. gordonii latex (1000 ppm), exhibited lesser feeding deterrence relative to naïve insects. Experienced female moths actually preferred to lay eggs on treated rather than control leaves. There was no observed transfer of behavioral preferences from experienced parents to their offspring. Our results suggest that moths may be acquiring oviposition preferences from larval feeding experience as described by Hopkins’ host selection principal (HHSP) or through chemical legacy. 相似文献
7.
Increased nitrogen availability influences predator–prey interactions by altering host-plant quality
Little is known about how plant nutritional and defensive qualities interact to influence predator–prey interactions. To address
this need, we provided the neo-tropical milkweed, Asclepias curassavica, with two levels of nitrogen availability and examined how altered host-plant quality influenced the responses of a specialist
aphid, Aphis nerii, and a coccinellid predator, Harmonia axyridis. Aphis nerii uses A. curassavica for multiple resources, including nutrition and sequestration of cardenolides for defense against natural enemies. Increased
nitrogen availability improved A. curassavica quality by decreasing carbon-to-nitrogen (C:N) ratios and cardenolide concentrations, resulting in A. nerii that also had lower C:N ratios and cardenolide concentrations. Aphis nerii population growth was higher on plants with high nitrogen availability, compared with aphids on plants with low nitrogen
availability. In no-choice feeding trials, Harmonia axyridis consumed more high C:N ratio aphids, suggesting a potential compensatory response to reduced aphid nutritional quality. Additionally,
H. axyridis were able to consume more low-quality aphids at the expense of increasing exposure to increased cardenolide concentrations,
suggesting that interactions between H. axyridis and A. nerii may be strongly influenced by prey nutritional quality. This work highlights the need to consider how variation in plant
quality influences herbivore nutritional and defensive quality when examining mechanisms that influence predator–prey interactions. 相似文献
8.
Louis Hautier Jean-Claude Grégoire Jérôme de Schauwers Gilles San Martin Pierre Callier Jean-Pierre Jansen Jean-Christophe de Biseau 《Chemoecology》2008,18(3):191-196
Summary. Under laboratory conditions, the multicolored Asian lady beetle, Harmonia axyridis is well known as an intraguild predator of other ladybirds. However the real impact of this exotic species on native species
was poorly investigated in the field. Because many ladybird species produce alkaloids as defensive compounds, we propose here
a new method of intraguild predation monitoring in coccinellids based on alkaloid quantification by GC-MS. In laboratory experiments,
adaline was unambiguously detected in fourth instar larvae of H. axyridis having ingested one egg or one first instar larva of Adalia bipunctata. Although prey alkaloids in the predator decreased with time, traces were still detected in pupae, exuviae and imagines of
H. axyridis having ingested one prey when they were fourth instar larvae. Analysis of H. axyridis larvae collected in two potato fields shows for the first time in Europe the presence of exogenous alkaloids in 9 out of
28 individuals tested. This new method of intraguild predation detection could be used more widely to follow the interactions
between predators and potential chemically defended insect preys. 相似文献
9.
Summary. The furoquinoline alkaloids skimmianine and dictamnine were tested for effects on the feeding and growth of larvae of the
generalist lepidopteran, Spodoptera litura. Skimmianine was further investigated for toxic and phototoxic effects on the larvae of Trichoplusia ni, also a generalist species. In feeding experiments with S. litura, growth and consumption of larvae decreased with increasing concentration of furoquinolines; skimmianine caused a greater
reduction in growth than dictamnine. In T. ni, dietary skimmianine reduced growth and consumption; when administered topically, it significantly reduced consumption but
without a concomitant reduction in growth. Phototoxicity of skimmianine was not apparent in T. ni because UV light failed to increase the negative effects of the alkaloid on larvae. 相似文献
10.
Resistance of the generalist moth Trichoplusia ni (Noctuidae) to a novel chemical defense in the invasive plant Conium maculatum 总被引:1,自引:0,他引:1
Summary.
Conium maculatum is an apiaceous species native to Eurasia that is highly toxic to vertebrates due to the presence of piperidine alkaloids,
including coniine and γ-coniceine. More than 200 years after invading the United States this species remains mostly free from
generalist insect herbivores. The presence of novel chemical defenses in the introduced range could provide invasive species
with a competitive advantage relative to native plants. The cabbage looper (Trichoplusia ni) is a generalist lepidopteran found throughout the US that occasionally feeds on C. maculatum. We evaluated the toxicity of piperidine alkaloids to T. ni and determined putative resistance mechanisms, both behavioral and physiological, that allows this insect to develop successfully
on C. maculatum foliage. T. ni larvae raised on diets enriched with coniine and γ-coniceine showed a decrease in consumption and longer development time,
but no effects on growth were found at any alkaloid concentration. In a diet choice experiment T. ni larvae showed no avoidance of alkaloid-enriched diets, suggesting that the deterrence produced by alkaloids was related to
a post-ingestive metabolic response. The ability of T. ni to consume diets high in alkaloid content could be due to at least three different mechanisms: 1) a decreased consumption
rate, 2) efficient excretion of at least 1/3 of ingested alkaloids unmetabolized in frass, and 3) partial detoxification of
alkaloids by cytochrome P450 s, as shown by the decreased larval growth in the presence of piperonyl butoxide, a P450 inhibitor.
Even though T. ni tolerates C. maculatum alkaloids, the use of this species as a host plant could be ecologically disadvantageous due to prolonged larval growth and
thus increased exposure to predators. Novel plant secondary compounds do not guarantee increased resistance to generalist
herbivores. 相似文献
11.
Summary. The effect of rearing larvae of Trichoplusia ni on
individual feeding deterrents or on binary mixtures of deterrents
on their subsequent gustatory sensitivity was measured
in paired choice leaf disc bioassays. Our working hypothesis
was that mixtures of antifeedants (pure allelochemicals)
would mitigate decreased feeding deterrent response following
prolonged exposure in this generalist herbivore. Neonate
larvae were reared on cabbage leaves treated with individual
feeding deterrents (digitoxin, thymol, toosendanin or xanthotoxin),
or with binary mixtures of these until the third instar.
Feeding deterrent responses to each antifeedant or mixture
was then determined in a leaf disc choice bioassay. All of the
mixtures produced additive deterrence when presented to
naïve larvae. Larvae reared on individual antifeedants
showed a significantly decreased feeding deterrent response
(except to digitoxin), whereas larvae reared on binary mixtures
of antifeedants did not show a decreased feeding deterrent
response to any of them. Such mixtures were synergistic
in terms of their feeding deterrence to experienced larvae.
Our experiment supports the hypothesis (Jermy 1986) that
mixtures of deterrents can prevent decreased feeding deterrent
response following prolonged exposure, and provides one
explanation for the multiplicity of chemical defenses found
in many plants. 相似文献
12.
Effects of hydrolysable tannins on a herbivorous insect: fate of individual tannins in insect digestive tract 总被引:2,自引:0,他引:2
Summary. We investigated the effects of four chemically characterised galloylglucoses (GGs, a subgroup of hydrolysable tannins) and
their hydrolysis product, gallic acid (GA), on consumption and performance of larvae of the autumnal moth Epirrita autumnata. Larvae were fed with birch (Betula pubescens) leaves that had been painted individually with each of the compounds at two levels, 5 and 20 mg/g. In addition, we investigated
the fates of the leaf-painted GGs and GA in the E. autumnata digestive tract by comparing phenolics in leaves consumed and in faeces. In general, GGs reduced leaf consumption by E. autumnata during the second and fourth instars, although there was high compound- and instar-specific variation. However, GGs did not
affect the leaf consumption rates by the most voracious fifth instar larvae. This resulted in approximately the same loss
of total biomass by the experimental tree, regardless of the nature and level of GGs enriched to its foliage. The characteristic
fate of hydrolysable tannins, i.e. hydrolysis, was evidenced in the larval digestive tract for three of the four leaf-painted
GGs. In addition to hydrolysis, the almost total absence of GGs in larval faeces was presumably related to the oxidation of
GGs. The dose-dependent excretion percentage of ingested GA showed that it's faecal content should not be used, although it
commonly is, to calculate the level of GG hydrolysis. Moreover, by comparing the non-uniform appearance of faecal tetragalloylglucoses,
whether ingested as such or hydrolysed from pentagalloylglucose, we concluded that a major part of oxidation of GGs occurs
before their hydrolysis in the digestive tract of E. autumnata. Criticism against the common use of tannic acid, a heterogeneous mixture of GA and GGs, in ecological studies is presented.
Received 15 May 2002; accepted 16 July 2002 相似文献
13.
Within a species, ontogenetic and genetic variation in defensive chemistry can provide the basis for natural selection from
different predator types. The osmeterial chemistry of fifth (last) instar Papilio glaucus caterpillars is known to differ qualitatively from the composition of early instar caterpillars. However, the osmeterial
chemistry of early instar caterpillars has not been thoroughly characterized and may change as the caterpillars undergo their
first three molts. We have used GC/MS to identify a suite of about 50 different terpene compounds in the osmeterial secretions
of P. glaucus caterpillars, and found the relative amounts of these compounds changed significantly with each molt. These quantitative
changes preceded the more dramatic qualitative switch to the production of 2-methylbutyric and isobutyric acids after the
molt to the fifth instar. We also examined the effects of diet and genetic background on the relative quantities of 15 terpenes
present in the secretions of third instar caterpillars. Parentage was found to affect the percentages of many more of the
individual components than did diet, although both exerted an effect. The ontogenetic and genetic variations in the composition
of the osmeterial secretions appear to have an effect on would-be predators. In the laboratory, terpene secretion was found
to discourage attack by ants, whereas the switch from terpene to acid production rendered the caterpillars less palatable
to a larger predator, the green anole. In the field, the presence of functional osmeteria did not seem to dramatically increase
survival in a field study, and only a small, non-significant advantage was seen. Similarly, field data was suggestive that
parentage might affect the likelihood of survival in a natural setting, but the stage of the caterpillar and the field site
significantly affected survivorship. Further studies with greater replicates will be needed to determine whether and to what
extent chemical differences in osmeterial components as well as behavior contribute to differences in outcomes in the field. 相似文献
14.
Summary. Polyphagous caterpillars of the giant geometer
Biston robustum resemble the twigs of their respective food
sources in color and shape. Common predatory ants, including
Lasius and
Formica, were often observed to freely prowl directly on caterpillars bodies, even after antennal contact.
This suggests that the cuticular chemicals of the caterpillars
resemble those of the twigs of the foodplants, so we analyzed
both by GC and GC-MS. The chemical compositions
differed among caterpillars fed on a cherry, Prunus yedoensis,
a chinquapin Castanopsis cuspidata, and a camellia Camellia japonica. The cuticular chemicals of the caterpillars
resembled those of their corresponding food sources.
When the caterpillar diets were switched from the cherry to
camellia or chinquapin at the 4th instars, the caterpillars
cuticular chemicals changed after molting to resemble those
of their respective foods. Caterpillars also changed their
cuticular chemicals when they perched on cherry twigs and
fed on camellia or chinquapin leaves, but not when they
perched on camellia or chinquapin twigs and fed on cherry
leaves. The chemical similarities between the caterpillars
and the twigs were due to the digestion of host leaves, which
indicates that this is a diet-induced adaptation. 相似文献
15.
Summary Various butterflies select young foliage on which to lay their eggs; volatiles emitted by young and old leaves have been compared (by sorption enrichment, followed by GC-MS) to gauge possible qualitative and quantitative differences between the two age groups. The plants investigated are cabbage (Brassica oleracea), two milkweeds (Asclepias syriaca andA. curassavica), the bitter orange (Citrus aurantium) and the lime (C. aurantiifolia). The chemical compounds identified belong to three classes, isoprenoids, fatty acid derivatives and benzenoids. Quantitative differences were found between young and old leaves, of which a few may be characteristic of young leaves only. Thirty-four single trials withDanaus plexippus exposed to volatiles from young and old leaves are recorded. 相似文献
16.
Summary. Young larvae of Adalia bipunctata search an area more intensively when exposed to the odour from other larvae feeding on aphids than when exposed only to the
odour of aphids. In an olfactometer young larvae were significantly attracted either to the odour of crushed aphids or larvae
feeding on aphids, but not to that of aphids, larvae, larvae plus aphids or larvae feeding on an artificial diet. That is,
the change in searching behaviour appears in response to a volatile released by aphids when attacked. The odour released by
crushed aphids is made up entirely of aphid alarm pheromone, β-farnesene. It is likely that the adaptive significance of this
response is that it increases the ability of larvae to locate larvae that have already caught prey. By sharing the aphid kill
of another larva it is likely that a first instar ladybird larva greatly increases its probability of surviving to the next
instar. It is suggested that this social feeding is facilitated by egg clustering, which also may additionally account for
why aphidophagous ladybirds lay their eggs in clusters.
Received 28 February 2000; accepted 24 March 2000 相似文献
17.
Anna K. Hundsdoerfer Jeannette Ndaya Tshibangu Bernhard Wetterauer Michael Wink 《Chemoecology》2005,15(4):261-267
Summary. The larvae of the hawkmoth species Hyles euphorbiae have a conspicuous aposematic colouration and show gregarious behaviour. It has thus been suggested that they sequester phorbol
esters from their food plants which include different species of the genus Euphorbia (Euphorbiaceae) for chemical protection against predators. To test this hypothesis in more detail, we fed larvae an artificial
diet with three doses of 12-tetradecanoyl-phorbol-13-acetate (TPA), then examined the faeces and the larval tissues, such
as integument, haemolymph and gut of the caterpillars for the presence of TPA. In order to determine the ability of the larvae
to detoxify phorbol esters, other larvae were directly injected with a TPA solution and analysed in the same manner. Our study
indicates that the larvae of Hyles euphorbiae do not sequester phorbol esters. Upon oral application TPA was not found in the larval integument or the haemolymph. Instead,
it was mostly metabolised (about 70–90%). Nevertheless, about 10-30% were retained and recovered in the faeces. The larvae
were also able to metabolise and thus detoxify the phorbol ester when TPA was injected directly into the body. These hawkmoth
caterpillars are relatively large and have a gut full of plant material, which they regurgitate into the direction of the
predator when attacked in nature. Since phorbol esters are very potent toxins and irritants, we postulate that the gut content
(and especially the plant slurry disgorged as regurgitant from the anterior gut) alone could be aversive for a potential predator,
even if some metabolism has taken place. Thus, although H. euphorbiae caterpillars do not actively sequester phorbol esters, their aposematic colouration appears to be based on chemical defence
through phorbol esters retained in the gut. 相似文献
18.
The zoeal larvae of brachyuran crabs must feed soon after hatching on a diet that includes large micro- and mesozooplankton
in order to satisfy nutritional requirements. However, newly hatched larvae have been shown to ingest a variety of dinoflagellates,
perhaps using microbial carbon sources to sustain them until they encounter more favored prey. Ingestion of dinoflagellates
by larval crabs has been documented previously under conditions in which the larvae were exposed to algae provided in monoculture
or in defined mixtures of cells. We report here on experiments conducted on the hatching stage of five crab species to determine
if ingestion of dinoflagellates occurred when they were provided in combination with Artemia sp. nauplii or after a period of feeding on mesozooplankton. Quantitative measurements of chl a in the larval guts provided evidence of ingestion of algal cells. Active ingestion of the dinoflagellate Prorocentrum micans at specified intervals during an extended feeding period was determined on larvae of two crab species using fluorescently
labeled cells provided for brief periods at prescribed time intervals. Stage 1 larvae of four of the five crab species ingested
dinoflagellates when they were provided in combination with nauplii and larvae of all five species ingested cells after feeding
solely on nauplii for 24 h. Ingestion of algal cells was first evident in the larval guts after 6 h of feeding at both low
(200 cell ml−1) and high (1,000 cells ml−1) prey densities. Higher prey densities resulted in higher gut chl a. Larvae continuously exposed to dinoflagellates actively ingested cells at every 3 h interval tested over a 36 h period.
Results confirm previous studies that larvae will ingest dinoflagellates even when they are encountered in a mixed prey field
or when having previously fed. Ingestion of cells may occur on a continual basis over time. 相似文献
19.
Edward M. Jhee Keri L. Dandridge Arthur M. Christy Jr. A. Joseph Pollard 《Chemoecology》1999,9(2):93-95
20.
Ethyl alcohol, acetone, and petroleum ether extracts of three plant species belonging to three different botanical families [Strychnos nux-vomica (Loganiaceae), Euphorbia lathyrus (Euphorbiaceae), and Datura stramonlum (Solanaceae)], a chemical insecticide; profenofos and their combinations were tested against second and fourth instars of Spodoptera littoralis under lab conditions. Results revealed that the ethanol extract of S. nux-vomica was the most effective among all plant extracts, where the corrected mortality% were 92, 81, 58, and 27% to 2nd instar and 89, 74, 34, and 11% to 4th instar at concentrations 0.5, 0.25, 0.125, and 0.0625%, respectively. Calculated LC50's were 0.11, 0.22, and 0.34% to 2nd instar and 0.17, 0.37, and 0.52% to 4th instar for ethanol, petroleum ether, and acetone extracts, respectively. Acetone extracts of all plants were of lower effect. The chemical insecticide profenofos displayed higher efficacy than plant extracts (LC50 = 0.002 and 0.003% for S. littoralis 2nd and 4th larval instars, respectively). The co-toxicity factor reached 76 and 60 when mixing S. nux-vomica + profenofos and D. stramonlum + profenofos at ratio 1:1 against S. littoralis 2nd instar larvae, thus indicating a potentiating effect. While treatment of the 4th instar larvae by the same mixtures resulted in a co-toxicity factor below 20 at all mixing ratios indicating, only, an additive effect against this instar. 相似文献