Interaction between Podisus maculiventris and Harmonia axyridis two predators used in augmentative biological control in greenhouse crops

Intraguild predation (IGP) betweenthe pentatomid Podisus maculiventris(Say) and the coccinellid Harmoniaaxyridis (Pallas) in the absence or presenceof the extraguild prey Spodopteralittoralis (Boisduval) and Myzuspersicae (Sulzer) was studied in thelaboratory. Interactions were asymmetric infavor of the pentatomid. Podisusmaculiventris readily fed upon eggs and larvaeof H. axyridis, but adult beetles wererarely attacked. Success of attacks by P.maculiventris was stage dependent, fourthinstars and adults being more successful inkilling ladybeetle larvae than second instars.Attacks by H. axyridis on the pentatomidwere rare and none of them were successful. Theeffect of introducing extraguild prey on thelevel of IGP was tested both in petri dishesand on caged sweet pepper plants. Whensufficient numbers of S. littoralislarvae were present to satiate the pentatomid,predation on H. axyridis larvae decreasedsignificantly, indicating that the coccinellidis a less preferred or less vulnerable prey.When the aphid M. persicae was presentedas extraguild prey, levels of IGP were notaltered. Nymphs of P. maculiventrissuccessfully completed development whenexclusively fed on larvae of H. axyridis,but developmental time was longer than onlepidopteran prey. No pentatomid nymphs reachedadulthood on aphids alone. IGP by P.maculiventris on H. axyridis may be ofsome importance in greenhouse crops, where bothpredators are being used increasingly inaugmentative biological control programs.Nonetheless, it is expected that in practicelarger larvae and adults of H. axyridiswill escape most attacks by the pentatomid.     

Populations of Predaceous Natural Enemies Developing on Insect-Resistant and Susceptible Tomato in North Carolina

Naturally occurring populations of immature and adultGeocoris punctipes,adultColeomegilla maculataand immature coccinellids were monitored on field-grown tomato lines susceptible and resistant toManduca sextaandHelicoverpa zea. Helicoverpa zeaandHeliothis virescenseggs and small larvae that serve as prey for these predators also were monitored. MoreH. zeaandH. virescenseggs and small larvae were found on resistant than on susceptible plant lines. However, similar populations of largeH. zeaandH. virescenslarvae were found on resistant and susceptible plants. The number of adultGeocoris punctipes,adultColeomegilla maculataand immature coccinellids on resistant plants was always as high or higher than the number on susceptible plants. The data demonstrate no incompatibility of host-plant resistance with biological control provided by these predaceous insects, but indicate that the number ofG. punctipesand coccinellids required to provide effective biological control may develop too late in the season to be of practical value. Large populations of stilt bugs (Jalysus wickhami,Hemiptera: Berytidae) and spiders were observed to occur earlier in the growing season than eitherG. punctipesor coccinellids and may be a significant source of mortality forH. zeaeggs and small larvae.     

Negative dietary effects of Colorado potato beetle eggs for the larvae of native and introduced ladybird beetles

Aphidophagous ladybird beetles (Coleoptera: Coccinellidae) are attracted to and feed heavily on aphids, but many species will also feed opportunistically on other prey that they encounter. In potatoes (Solanum tuberosum L.) in Washington State, USA, coccinellids feed on both green peach aphids (“GPA,” Myzus persicae Sulzer) and eggs of the Colorado potato beetle (“CPB,” Leptinotarsa decemlineata Say). The guild of aphidophagous ladybirds includes two native species, Hippodamia convergens Guérin-Méneville and Coccinella transversoguttata Brown. Recently, an introduced species, Coccinella septempunctata L., has invaded and apparently displaced its native congener. A second exotic, Harmonia axyridis Pallas, has colonized the area and is becoming more abundant. We compared larval development of each species on a monotypic diet of GPA, a monotypic diet of CPB eggs, or a mixed diet of both GPA and CPB eggs. Our goal was to answer two questions: (1) do larvae of the four ladybird species benefit from including CPB eggs in their diet and (2) do the four ladybird species differ in their ability to utilize CPB eggs as prey? No larva of any species completed development on a pure diet of CPB eggs, and survivorship was highest for all species when they fed on a pure diet of GPA. One native species, H. convergens, and one exotic species, H. axyridis, exhibited significantly lower survivorship on a mixed diet of both CPB eggs and GPA, compared to a pure GPA diet; H. axyridis also took longer to develop from egg to adult when both prey were provided. Survivorship of the two Coccinella spp. was not altered by the inclusion of CPB eggs with GPA, although CPB eggs lengthened the development time of C. transversoguttata. Adult size was not consistently affected by diet for any of the coccinellids. Overall, no ladybird species benefited from the inclusion of potato beetle eggs in its diet. The two Coccinella species responded similarly to the inclusion of CPB eggs, and so we would not expect any difference in the success of coccinellid larval development in potato fields following the replacement of C. transversoguttata by C. septempunctata. Hippodamia convergens and H. axyridis, the two species whose survivorship was depressed by combining CPB egg and aphid prey, were also the two species that consumed the greatest number of CPB eggs during successful larval development. A comparison of total egg consumption by each species cohort suggested that displacement of the other species by H. axyridis would not alter CPB biological control, because the higher per capita feeding rate by H. axyridis larvae compensated for individuals’ greater mortality risk on a diet including CPB eggs.     

Suitability of greenbugs, cotton aphids, andHeliothis virescens eggs for development and reproduction ofOrius insidiosus

Development, fecundity, and longevity of the predator,Orius insidiosus (Say) (Heteroptera: Anthocoridae), when reared on greenbug [Schizaphis graminum (Rondani)], cotton aphid (Aphis gossypii Glover), or eggs of tobacco budworm [Heliothis virescens (F.)] with green beans or water were examined. Developmental time was shortest when predators were reared onH. virescens eggs and beans and longest when reared on cotton aphids and water. Predators were most fecund when fedH. virescens eggs. The inclusion of beans in the nymphal diet further enhanced fecundity when fed eggs. Longevity of both females and males was significantly shorter when reared on aphids than on eggs. Beans in the nymphal diet enhanced longevity of female predators only in combination with budworm eggs. FemaleO. insidiosus were largest when reared onH. virescens eggs. Addition of green beans in aphid treatments resulted in increased size ofO. insidiosus when compared to aphids and free water.     

The effect of rearing the ladybirdHarmonia axyridis onEphestia kuehniella eggs on the response of its larvae to aphid tracks

Larvae ofHarmonia axyridis Pallas (Col., Coccinellidae) exhibited two walking patterns during prey search. Extensive search occurred when searching for prey patches and was characterized by long linear paths and a fast speed. Intesive search, which appeared after the ingestion of a prey in a patch, resulted from a lowering of the linear speed and an increase in the number of stops and angular speed. When larvae reared on the aphidAcyrthosiphum pisum Harris (Hom., Aphidae) crossed an artificial substratum previously contaminated by this prey, they changed their path direction and adopted intensive search. They probably perceived aphid odor tracks and consequently modified their walking pattern. This gustatory capacity probably allowed very mobile larvae to locate prey patches more rapidly and improve encounter with preys in every patch.H. axyridis larvae reared on a substitute prey, the eggs ofEphestia kuehniella Zeller (Lep., Pyralidae), for more than a hundred generations, also changed their path orientation but retained extensive search. The weak response of these larvae to aphid tracks may have resulted from either a decrease in their sensitivity to gustatory aphid stimuli or their difficulty in associating aphid odor with aphid presence. These larvae needed more time and more preliminary encounters than larvae reared on aphids before catching prey.     

Fecundity and oviposition ofEucelatoria bryani, a gregarious parasitoid ofHelicoverpa zea andHeliothis virescens

We examined longevity, fecundity, and oviposition strategies ofEucelatoria bryani Sabrosky (Diptera: Tachinidae), a gregarious endoparasitoid ofHelicoverpa zea (Boddie) andHeliothis virescens (F.) (Lepidoptera: Noctuidae). Longevity of adult femaleE. bryani was not related to body size. In contrast to longevity, largerE. bryani females had greater potential fecundity than smaller females, as determined by the number of embryonated eggs present in the common oviduct. However, female parasitoid size did not affect primary clutch size (number of eggs deposited in a host). Because embryos in eggs located in the ovisac were larger than those located elsewhere in the common oviduct, maximum primary clutch size may be physiologically limited by the number of fully mature eggs a female has available at one time.E. bryani females adjusted primary clutch size in response to host size, for bothH. zea andH. virescens. This adjustment appears to be adaptive because females did not overexploit hosts by depositing more larvae than a host could support. Adult emergence was not related to host size. Although host weight positively influencedE. bryani progeny weight, increases in progeny size with host size were counterbalanced by increases in primary clutch size with host size.     

Effects of Recombinant Baculoviruses on Three Nontarget Heliothine Predators

Genetically engineered baculoviruses, relative to their wild-type progenitors, have successfully improved the time-to-kill of these arthropod-specific biopesticides. Beneficial arthropods that prey on targeted pest insects are likely the first nontarget organisms to be adversely affected by the applications of such biopesticides. The goals of this project were to assess potential risks of the recombinant baculoviruses on Solenopsis invicta, Geocoris punctipes, and Hippodamia convergens, all of which are common predators of heliothines in Texas cotton. Four recombinant Autographa californica nuclear polyhedrosis viruses (AcNPV), one Helicoverpa zea nuclear polyhedrosis virus (HzNPV), and two corresponding wild-type NPVs were used in this risk assessment study. Risks associated with these baculoviruses were determined by possible shifts in predator life history traits (rate of food consumption, travel speed, fecundity, and survival) when fed prey infected with recombinant viruses compared to prey infected with wild-type viruses or to healthy prey. We also tested for possible transmission of these viruses by predators using the polymerase chain reaction (PCR). No significant shifts in life history characteristics were detected in predators fed Heliothis virescens larvae infected with any of the seven viruses. Viral DNA was discovered using PCR in 2.3% of fire ant workers, but not from any of the queens or eggs. In G. punctipes, 13.4% of adults and 0.5% of eggs scored positive for viruses. Twelve percent of H. convergens adults were found PCR positive. Residency in all three predators tested provides a pathway which could increase the persistence of recombinant viral particles in the environment and thus may produce an indeterminable amount of risk associated with their inadvertent movement.     

Larval oophagy in the ant <Emphasis Type="Italic">Amblyopone silvestrii</Emphasis> (Hymenoptera,Formicidae)

Summary Larvae pass through five instars in the temperate, subterranean ponerine ant, Amblyopone silvestrii. Field colonies displayed a large decrease in the number of eggs during mid-summer, despite the fact that queens maintained fully developed ovaries with mature eggs. Observations of laboratory colonies indicate that cannibalism by 1st and 2nd instar larvae caused this decrease in egg number. These instars consumed a total of 66–75% of eggs in the nest, with each larva consuming 2–3 eggs before molting to the 3rd instar. At that time the larvae began to feed on arthropods. The preferred prey of A. silvestrii consists of entire centipedes; the large size of these prey items relative to the size of early instar larvae makes it difficult for the larvae to feed on these prey. Additionally, workers of A. silvestrii do not engage in oral trophallaxis. Consequently, oophagy is a plausible method to feed these very small larvae.     

Functional response ofChrysopa carnea [Neur: Chrysopidae] larvae feeding onHeliothis virescens [Lep.: Noctuidae] eggs on cotton in field cages

The functional response of 3rd instarChrysopa carnea (Stephens) larvae feeding on 4 densities ofHeliothis virescens (F.) eggs was determined on caged cotton (Gossypium hirsutum L.).C. carnea larvae had a mean search rate of 1.08×10⁻⁵ ha/predator-day or 0.11 row-m/predator-day.      

Potential of adultOrius insidiosus [Hemiptera: Anthocoridae] as a predator of the fall armyworm,Spodoptera frugiperda [Lepidoptera: Noctuidae]

Orius insidiosus (Say) was observed to successfully prey on eggs and earlier instar larvae of the fall armyworm (FAW),Spodoptera frugiperda (J. E. Smith). Significantly more neonates of FAW were killed per 24 h than either 1, 2 or 3 d old larvae. Female and male predators exhibited a typical type-II functional response when preying on varying densities of eggs or neonates of FAW.      

Susceptibility of Helicoverpa zea and Heliothis virescens (Lepidoptera: Noctuidae) to Vip3A insecticidal protein expressed in VipCot™ cotton

Susceptibility of laboratory and field colonies of Helicoverpa zea (Boddie) and Heliothis virescens F. to Vip3A insecticidal protein was studied in diet incorporation and diet overlay assays from 2004 to 2008. Responses of field populations were compared to paired responses of University of Arkansas laboratory susceptible H. zea (LabZA) and H. virescens (LabVR) colonies. After 7 d of exposure, observations were made on number of dead larvae (M) and the number of larvae alive but remaining as first instars (L1). Regression estimates using M (LC₅₀) and M plus L1 (MIC₅₀) data were developed for laboratory and field populations. Susceptibility of laboratory and field populations exposed to Vip3A varied among different batches of protein used over the study period. Within the same batch of Vip3A protein, susceptibilities of laboratory colonies of both species (LabZA and LabVR) were similar. Field colonies were significantly more susceptible to Vip3A than the respective reference colonies of both species. Within field populations, susceptibility to Vip3A varied up to 75-fold in H. zea and 132-fold in H. virescens in LC₅₀ estimates. Variabilities in MIC₅₀s were up to 59- and 11-fold for H. zea and H. virescens, respectively.     

Predation capacity and prey preference of <Emphasis Type="Italic">Chrysoperla carnea</Emphasis> on <Emphasis Type="Italic">Pieris brassicae</Emphasis>

The predation capacity and prey preference of larvae of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) on eggs or larvae of Pieris brassicae (Linnaeus) (Lepidoptera: Pieridae) in the absence and presence of cabbage aphids as an alternative prey were evaluated in laboratory experiments at 25°C. Both instars preyed upon butterfly eggs and larvae as well as on cabbage aphids with the third instar being the most voracious. The lacewings had a strong preference for caterpillars to butterfly eggs. In the presence of the aphids the predation on P. brassicae eggs or larvae was either completely abandoned or reduced by about 70%, respectively, by second instar lacewings and either reduced by about 80% or maintained, respectively, by third instar lacewings. Both instars thus had a clear preference for aphids compared to eggs of P. brassicae. However, second instar lacewings preferred aphids to caterpillars whereas the opposite was the case for third instar lacewings. The results indicate that 3rd instar C. carnea has a potential as biocontrol agent against P. brassicae.     

Suitability of exotic and native lady beetle eggs (Coleoptera: Coccinellidae) for development of lady beetle larvae

Predation upon lady beetle (Coleoptera: Coccinellidae) eggs in the field is most often instances of egg cannibalism by larvae or adults while the majority of the remaining predation events upon coccinellid eggs is done by other species of Coccinellidae. Thus the recent introduction and establishment of Harmonia axyridis in the US could negatively affect native species of Coccinellidae via egg predation. However, little is known regarding the suitability of interspecific coccinellid eggs as a food source for larval development. In this study, it was found that native first or third instar Coleomegilla maculata and Olla v-nigrum larvae were incapable of surviving to the adult stage when provided solely exotic H. axyridis eggs. In stark contrast, H. axyridis larvae survived equally well when cannibalizing eggs or eating eggs of either native species. When C. maculata and O. v-nigrum were grouped as ‘native’ and compared with the exotic H. axyridis, more native eggs were attacked than exotic eggs and a higher percentage of eggs was attacked by H. axyridis larvae. Native and exotic larvae attacked a similar percentage of native eggs but native larvae attacked significantly fewer exotic eggs than did exotic larvae. These data suggest that H. axyridis may prey upon the eggs of these native species, when encountered in the field, compared with the likelihood of the native species preying upon H. axyridis eggs. Therefore, eggs of the native species C. maculata and O. v-nigrum will continue to be subjected to cannibalism and also to possible predation by other native species and the exotic H. axyridis.     

Feeding Fitness and Quality of Domesticated and Feral Predators: Effects of Long-Term Rearing on Artificial Diet

Predatory geocorids, Geocoris punctipes Say (Geocoridae: Hemiptera), that had been reared (domesticated) for over 6 years (60 continuous generations) on an artificial diet were compared with feral (F₁) counterparts to determine possible domestication-associated losses in predatory capabilities. Using adult female predators provided with either tobacco budworm larvae, Heliothis virescens F., or pea aphids, Acyrthosiphon pisum Harris, as prey, I measured predator weights, handling time with a single prey, amount extracted, consumption rate, and feeding (gut) capacity. Domesticated females were significantly smaller than ferals, weighing 4.53 mg versus 5.09 mg, respectively. Domestication did not significantly influence handling times, which averaged 131 (domesticated) and 122 min (feral) for predators feeding on H. virescens larvae and 106 (domesticated) and 94 min (feral) for G. punctipes feeding on A. pisum. Although there were significant differences in the weights of the two kinds of prey (H. virescens larvae being about twice as heavy as the A. pisum), both prey species exceeded the ingestion capacity of the predators. Amounts extracted by predators were 1.12 to 1.20 mg and were not significantly influenced by rearing background, prey biomass, or prey type. Consumption rates of 11.86 and 12.91 μg/min were nearly identical for both domesticated and feral predators regardless of prey species.     

Phosphorus-32 bioelimination by arthropod predators fed labeled eggs ofHeliothis virescens [Lep.: Noctuidae]

Adults ofGeocoris punctipes (Say),Tropiconabis capsiformis Germar,Nabis roseipennis Reuter andColeomegilla maculata (DeGeer) were confined inside petri dishes and fed phosphorus-32 (^32p)-labeledHeliothis virescens (F.) eggs. Observations of bioelimination of^32p over a 72 h period allowed derivation of equations for predicting the number ofH. virescens eggs ingested by each species. Twenty-four to 72 h after eggs were eaten, the percentages of^32p eliminated ranged from ca. 14% forG. punctipes to 42 % forT. capsiformis. Cautious use of the results will aid researchers in assessing predation on^32p labeledHeliothis. Publication N^o 5935. Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS 39762.     

Interference and competitive behaviour of the aphid predators,Chrysoperla carnea andCoccinella septempunctata in the laboratory

Interference and competition betweenChrysoperla carnea (Stephens) andCoccinella septempunctata L. was investigated in the absence and presence of aphid prey. When larvae of similar vigour encountered each other,C. carnea larvae were superior toC. septempunctata. Otherwise the larger of 2 individuals always killed the smaller. In the absence of preyC. carnea adults were attacked by their own 2nd and 3rd instar larvae as well as by 3rd instar larvae ofC. septempunctata. In all encounters the adults ofC. septempunctata were superior. Since the eggs ofC. carnea are protected to some extent by being on egg stalks, they were less susceptible to cannibalism and predation thanC. septempunctata eggs which are deposited in batches directly on plant leaves. In the presence of prey cannibalism and predation were reduced, especially between larvae. Only eggs and 1st instar larvae were endangered. In the present experimentsC. carnea showed a slight superiority overc. septempunctata. Paper presented at the 17th International Congress of Entomology held in August 20–26 1984 in Hamburg, F.R. Germany.     

Development and Reproduction of Ladybeetles (Coleoptera: Coccinellidae) on the Citrus Aphids Aphis spiraecola Patch and Toxoptera citricida (Kirkaldy) (Homoptera: Aphididae)

Seven species of Coccinellidae inhabiting citrus groves in Florida were evaluated for ability to develop and reproduce on the citrus aphids Toxoptera citricida (Kirkaldy) and Aphis spiraecola Patch. Choice tests performed with adults and larvae indicated that both aphid species were generally acceptable prey. Coccinella septempunctata L., Coleomegilla maculata fuscilabris (Mulsant), Coelophora inaequalis F., and Olla v-nigrum Mulsant were unable to complete development on either aphid. Hippodamia convergens Guerin larvae completed development on A. spiraecola with 68% survival; none survived on T. citricida. Only Cycloneda sanguinea (L.) and Harmonia axyridis Pallas completed development on both A. spiraecola (60 and 70% survival, respectively) and T. citricida (100 and 95% survival, respectively). Larval developmental time was shorter on T. citricida than on A. spiraecola, and resulting adults were heavier, differences being more pronounced in H. axyridis. Females of C. septempunctata, C. inaequalis, and O. v-nigrum produced viable eggs on T. citricida. O. v-nigrum did not produce eggs on A. spiraecola. Females of C. m. fuscilabris and H. axyridis produced no eggs on A. spiraecola and mostly infertile eggs on T. citricida. Female H. convergens laid twice as many eggs feeding on T. citricida as on A. spiraecola and egg viability was similar. C. sanguinea females laid similar numbers of eggs on both aphids, but eggs produced on A. spiraecola had higher fertility. Pollen added to the T. citricida diet temporarily improved the fertility of H. axyridis females, but not that of C. sanguinea females. C. sanguinea was judged the best candidate for augmentative biocontrol of T. citricida, the primary vector of citrus tristeza virus.     

Effects of Bt maize-fed prey on the generalist predator <Emphasis Type="Italic">Poecilus cupreus</Emphasis> L. (Coleoptera: Carabidae)

We investigated the effects of transgenic maize (Zea mays) expressing Bacillus thuringienses toxin (Bt maize) on larval and adult Poecilus cupreus carabid beetles in laboratory studies. In no-choice trials, neonate P. cupreus larvae were fed exclusively with Spodoptera littoralis caterpillars, which had been raised on Bt maize. S. littoralis raised on conventional maize or high quality Calliphora sp. pupae were fed to the beetle larvae in two control treatments. Bt-maize-fed caterpillar prey increased mortality to 100 within 40days. The experiment was repeated with 10-day-old beetle larvae. Bt treatment resulted in fewer pupae than in both controls, and in a higher mortality than in the Calliphora control. S. littoralis was suitable as exclusive prey in no-choice tests, at least for 40days, although prey quality seemed to be low compared to Calliphora pupae. The observed effects are most likely indirect effects due to further reduced nutritional prey quality. However, direct effects cannot be excluded. In the second part of the study, exposure of P. cupreus to Bt intoxicated prey was examined in paired-choice tests. Adult beetles were offered a choice between different prey conditions (frozen and thawed, freshly killed or living), prey types (S. littoralis caterpillars, Calliphorasp. pupae, cereal aphids) and prey treatments (raised on Bt or conventional maize). Living prey was preferred to frozen and dead prey. Caterpillars were only preferred to fly pupae and aphids when living. Prey treatment seemed to be least important for prey selection. The tests showed that P. cupreus ingested caterpillars readily and there was no evidence of them avoiding Bt containing prey, which means exposure in the field could occur. The presented protocols are a first step towards ecological risk assessment for carabid beetles.     

Relative consumption of three aphid species by the lacewing, Chrysoperla rufilabris, and effects on its development and survival

Relative consumption of three aphid species, Aphis gossypii Glover, Myzus persicae (Sulzer) and Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae), by larvae of the lacewing, Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae), was determined in the laboratory, together with effects on lacewing development and survival. Percentages of survival of C. rufilabris from first instar to adult eclosion were significantly different among lacewing larvae fed different aphid species. When larvae were fed A. gossypii and M. persicae, all larvae developed to adulthood. All larvae died prematurely when they were fed L. erysimi. Developmental duration of C. rufilabris larvae was significantly shorter when larvae were fed A. gossypii (18.0 d) than when larvae were fed M. persicae (19.2 d). The number of fourth instar aphids consumed during development by C. rufilabris larvae differed significantly among individuals fed different aphid species. Chrysoperla rufilabris consumed an average of 168 M. persicae, followed by 141.6 A. gossypii, and only 26.6 L. erysimi. The percentage of these total number of aphids consumed by each larval stadium of C. rufilabris varied significantly among aphid species. The percentage of A. gossypii consumed by each larval stadium was similar to that for M. persicae, 12.1 and 11.4% by the first instar, 15.7 and 13.1% by the second instar, and 72.2 and 75.5% by the third instar, respectively; whereas in the case of L. erysimi, 23.3% of the total number of aphids were consumed by the first instar, 30.1% by the second instar, and 46.6% by the third instar.     

Functional Response ofColeomegilla maculata(Coleoptera: Coccinellidae) to Colorado Potato Beetle Eggs (Coleoptera: Chrysomelidae)

A comparative study of the functional response ofColeomegilla maculataDeGeer (Coleoptera: Coccinellidae) fourth instars was conducted under laboratory, greenhouse, and field conditions. In the laboratory, individual larvae were placed in 9-cm petri dishes for 24 h, with 1, 3, 5, or 7 Colorado potato beetle (Leptinotarsa decemlineata[Say]) (Coleoptera: Chrysomelidae) egg masses. Each egg mass was standardized at 15 eggs. In the greenhouse and field,C. maculatalarvae were provided with an equivalent of 0.5 to 35L. decemlineataegg masses/m²of potato leaf. Fourth instars ofC. maculataexhibited a type II functional response toL. decemlineataeggs under laboratory, greenhouse, and field conditions. Predator search efficiency was inversely related with prey density. The maximum mean attack rate (8.7 eggs) byC. maculatalarvae in the field was about half the mean attack rate in the laboratory (17.6 eggs) and greenhouse (20.1 eggs). The difference in prey density between the laboratory and field seems to have been a major contributing factor in determining the rate of predation, whereas differences in environmental conditions (e.g., temperature and possible alternate food) may explain the differences observed in the predation rate in the greenhouse and field.