Preimaginal Development Research Articles

Influence of six aphid prey species on development and reproduction of a ladybird beetle, Coccinella septempunctata

Pre-imaginal development, immaturesurvival, and reproduction of a ladybird, Coccinella septempunctata Linnaeus, werestudied in response to six aphid species, Aphiscraccivora Koch, Aphis gossypii Glover,Aphis nerii Boyer de Fonscolombe,Lipaphis erysimi (Kaltenbach), Myzuspersicae (Sulzer) and Uroleuconcompositae (Theobald) to quantify theirrelative suitability as prey. Pre-adultdevelopment was shortest (13.93 ± 0.12 days)when fed on L. erysimi and longest(22.85 ± 0.10 days) on A. nerii. Immaturesurvival, adult emergence, growth index,relative growth rate, development rate, maleand female longevity, oviposition period,fecundity and hatching percent were maximal, i.e. 73.47 ± 0.89%, 90.07 ± 1.43%,8.62 ± 0.23, 1.52 ± 0.02, 0.07,81.10 ± 1.26 days, 85.70 ± 1.45 days,69.80 ± 1.32 days, 1764.10 ± 8.46,and 87.88 ± 1.05, respectively when C.septempunctata were fed on L. erysimi.The same parameters were minimal, i.e.43.86 ± 1.33%, 71.65 ± 2.75%,2.02 ± 0.08, 0.49 ± 0.02, 0.04,44.40 ± 1.39 days, 53.50 ± 1.00 days,16.40 ± 0.60 days, 203.20 ± 11.83, and48.68 ± 2.06, respectively on A. nerii. Theweights of different ladybird life stages weremaximal after feeding on L. erysimi and minimalon A. nerii. Regression analyses of thedata revealed linear relationships betweendevelopment rate and weight of adult; dailyprey consumption and relative growth rate; logweight of adult male and female; and longevityand fecundity of female. On the basis of thesefindings, the order of suitability of aphidspecies for C. septempunctata is L. erysimi >M. persicae > A. craccivora > A. gossypii >U. compositae > A. nerii. Thus, the presentinformation can be utilized for the massrearing of C. septempunctata by supplyingthe best food and can also help in theprediction of the relative abundance of theladybird on different aphid infestations in thefields.

Relation between the Level of Preimaginal Infestation by the Broodmite Varroa destructor and Adult Life Expectancy in Drone Honeybees (Hymenoptera: Apidae: Apis mellifera)

Varroa destructor Anderson & Trueman 2000 preferentially infests the drone brood of the European honeybee, Apis mellifera Linnaeus 1758. However, little is known about, how such infestations affect colony reproduction. The survival of drone honeybees was recorded as a function of different levels of Varroa infestation during their preimaginal development. In May and early June, drones emerging from uninfested brood cells lived a mean of 28 days. The life expectancy of parasitized drones was considerably shorter and depended on individual parasitic load. Since few infested drones lived till 12 days after emergence, when drones in Central Europe normally begin mating flights, varroatosis in Apis mellifera colonies significantly reduces the number of drones potentially participating in reproduction.

Effects of temperature and host on the pre-imaginal development of the parasitoid Diglyphus isaea (Hymenoptera: Eulophidae)

Abstract The development of Diglyphus isaea (Walker), a parasitoid of leafminers, was studied under laboratory conditions at four constant temperatures (15, 20, 25, and 30 °C) on the hosts Liriomyza trifolii (Burgess) and Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae). Parasitoid developmental time was found to be inversely related to temperature. At 15 °C, D. isaea took about 28 days to complete its development on L. huidobrensis and about 27 days on L. trifolii. In comparison, at 20 °C developmental time dropped to half on both species and the same happened from 20 to 30 °C. At 25 °C, parasitoid development was complete after about 10 days. At all tested temperatures and on both host species, the length of pupal stage of the parasitoid was slightly shorter than the egg + larva period. Linear regression and the Logan model were used to describe the relationship between developmental rate and temperature. For egg to adult development, female D. isaea required 161.8 degree-days (DD) above the theoretical threshold of 9.2 °C on L. trifolii and 165.0 DD above 9.3 °C on L. huidobrensis, and males required 151.4 DD above 9.5 °C on L. trifolii and 157.4 DD above 9.3 °C on L. huidobrensis. Optimum temperatures for total female and male development on L. trifolii were 33.3 and 32.3 °C, and on L. huidobrensis 32.6 and 31.0 °C, respectively. The effects of host, sex, and temperature on parasitoid size were studied. Significant sex–temperature, host–temperature, and host–sex–temperature interactions were found. The host species was found to affect female parasitoid size differently based on temperature.

Comparative Life History ofLiriomyza trifoliiandLiriomyza huidobrensis(Diptera: Agromyzidae) on Beans: Effect of Temperature on Development

The influence of four constant temperatures (15, 20, 25, and 30°C) on development time and survivorship of Liriomyza trifolii (Burgess) and Liriomyza huidobrensis (Blanchard) was studied in laboratory experiments. L. huidobrensis required more time for embryonic development at 25 and 30°C, and less time at 15°C, compared with L. trifolii; at 20°C there were no differences between the two species. Larval development time for L. huidobrensis was longer than for L. trifolii at 20, 25, and 30°C. At 15°C no differences were detected. Pupal development of L. huidobrensis was always faster at 15, 20, and 25°C than that of L. trifolii. Total preimaginal development time was quicker at 15 and 20°C in L. huidobrensis than in L. trifolii; at 25°C no significant differences were found. Highest survival of L. trifolii (68%) occurred at 20°C, while that of L. huidobrensis (61%) occurred at 15°C. At 30°C no adults of L. huidobrensis emerged. The estimated lower threshold temperatures for egg, larva, pupa and total development of L. huidobrensis ranged between 7.3 and 8.1°C, and they were always lower than L. trifolii thresholds, which ranged between 9.9 and 10.7°C. The Logan model was used to describe the relationship between development rate and temperature. The quantification of development times presented in this study, combined with fecundity under different temperatures, could be incorporated into a phenological model that will aid in predicting population charges of leafminers.

Thermal Requirements for Development of the Polyphagous PredatorMacrolophus pygmaeus(Hemiptera: Miridae)

The effect of temperature on the duration of embryonic and nymphal development as well as on the preoviposition period of the polyphagous predator Macrolophus pygmaeus Rambur was studied in the presence and in the absence of prey on eggplant, pepper-plant, and tomato at 15, 20, 25, 27.5, 30, and 35°C, with 65 ± 5% RH and photoperiod of 16:8 (L:D) h. The aphid Myzus persicae (Sulzer) was used as prey on eggplant and pepper-plant and the whitefly Trialeurodes vaporariorum (Westwood) on tomato. The data obtained were used for the estimation of the thermal requirements of this predator. The temperature threshold for egg development was found as 7.61 and 6.92°C, for nymphal development in the presence 8.74 and 9.19°C and in the absence of prey 8.21 and 9.29°C, for preimaginal development 8.68 and 8.79°C, for preoviposition 7.58 and 6.96°C, and finally for egg-to-egg development 8.48 and 8.51°C on eggplant with M. persicae and on tomato with T. vaporariorum, respectively. On pepper-plant the temperature threshold for nymphal development was 8.26 and 8.23°C in the presence and in the absence of prey, respectively. The values of temperature threshold for development of the various nymphal stages were similar. It was also found that the slopes of the linear regressions between the rate of nymphal development and temperature were not significantly different among the different host plants in the presence and in the absence of prey. Also, the slopes of the linear regressions concerning the development of each nymphal stage with temperature were not found to differ significantly among the host plants in the presence and in the absence of prey. The thermal constant for egg development was estimated as 177 and 182, that for nymphal development in the presence 269 and 253 and in the absence of prey 332 and 306, for preimaginal development 439 and 431, for preoviposition 100 and 98 and finally that of egg-to-egg development 541 and 533 degree-days when fed on M. persicae on eggplant and on T. vaporariorum on tomato, respectively. On pepper-plant the degree-days for nymphal development was 280 and 361, in the presence and in the absence of prey, respectively. The temperature threshold for development was not found to differ among the host plants in the presence and in the absence of prey. However, the degree-days were significantly different between the presence and absence of prey on each host plant; the thermal constant in the absence of prey was estimated as an average of 1.21 times of that in the presence of prey. The results show that M. pygmaeus can establish, develop, and oviposit even in the absence of prey in relatively low temperatures and hence it can be released early in the season for an earlier and more effective control of whiteflies and aphids on vegetables.

Selected Life-History Traits of Black Soldier Flies (Diptera: Stratiomyidae) Reared on Three Artificial Diets

Hermetia illucens (L.) was reared on three larval diets to determine their effects on preimaginal development and selected adult life-history traits. Prepupal and adult characteristics were examined for individuals reared on each diet and compared with field-collected prepupae and corresponding emergent adults. Diet did not significantly influence development or survivorship to the prepupal stage. However, adult emergence for all diets was significantly less than that determined for the wild population. Development time from egg to adult for individuals reared on the diets at 27°C ranged from 40 to 43 d with the larval stage lasting 22–24 d. We observed >96% larval survivorship to the prepupal stage and 21–27% adult emergence. Females accounted for 55–60% of emergent adults across treatments. Specimens reared on each diet were reduced in size, longevity, and calorie content in comparison to specimens from the wild population. Males within diet treatments and field-collected specimens were significantly smaller than females and emerged 1–2 d before females. Additionally, males reared on the diets and provided water lived for 9 d, whereas females lived for 8 d. This information indicates the diets might be used for rearing soldier flies. However, further refinement is needed to produce adults similar to those found in nature.

Diapause in the egg parasitoid Trichogramma cordubensis: role of temperature

The role of temperature in the induction of diapause in Trichogramma cordubensis (Hymenoptera: Trichogrammatidae), under controlled laboratory conditions, was investigated using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs as hosts. Results indicate that prestorage temperatures and the duration of exposure of the parasitoids to these temperatures affected the induction of diapause. It was possible to induce diapause in prepupae of T. cordubensis by exposing the preimaginal stages (prior to the prepupal stage) to 10°C for at least 30 days, but adults emerged without diapause when the duration of exposure was of only 10 or 20 days. Parasitoids failed to enter diapause when prestorage temperatures were 7 or 12°C, regardless of the duration of exposure. However, at these two temperatures, preimaginal development of T. cordubensis was delayed, allowing short-term storage (40 days at induction temperatures followed by 30 days at 3°C) by keeping parasitoids in quiescence without reducing the percentages of adult emergence. Good percentages of adult emergence after long-term low-temperature storage (30 or 40 days at 10°C followed by six months at 3°C) occurred only when T. cordubensis was in diapause. The long-term storage of parasitoids in diapause allows an enlargement in the mass rearing potentialities of this species for future biological control releases by allowing producers to stockpile the parasitoids for release in the field season.

Prey Suitability of Galerucella pusilla Eggs for Two Generalist Predators, Coleomegilla maculata and Chrysoperla carnea

The leaf beetle, Galerucella pusilla, is an introduced natural enemy of purple loosestrife, Lythrum salicaria, in North America. The suitability of G. pusilla eggs for development and survival of Chrysoperla carnea and Coleomegilla maculata was quantified by measuring preimaginal development, survival, and adult weight. Individual first-instar predators were assigned to one of two diets: G. pusilla eggs or a diet of Ephestia kuehniella eggs and pea aphids ( Acyrthosiphon pisum ) alternated every 24 h. Chrysoperla carnea and C. maculata larvae that fed on G. pusilla eggs had lower survival rates, longer developmental times, and reduced adult weight. Galerucella pusilla eggs were not suitable prey for 95% of C. maculata larvae, but 37% of C. carnea larvae completed development on G. pusilla eggs. Because G. pusilla eggs may be utilized by these predatory species as alternative prey during periods of low availability of suitable prey, this predation could affect the biological control of L. salicaria .

Modelling population dynamics of Orius laevigatus and O. albidipennis (Hemiptera: Anthocoridae) to optimize their use as biological control agents of Frankliniella occidentalis (Thysanoptera: Thripidae).

ORIUS LAEVIGATUS: (Fieber) and O. albidipennis (Reuter) play an important role in the control of Frankliniella occidentalis (Pergande) in crops and natural vegetation in the Mediterranean area. The biological parameters of the two anthocorids were studied and modelled in relation to temperature to optimize their use in thrips control programmes. Development times and reproductive parameters of O. laevigatus and O. albidipennis were determined at 20, 25, 30 and 35 degrees C. Pre-imaginal development times ranged from 34.6 and 37.2 days at 20 degrees C to 12.3 and 10.2 days at 35 degrees C in O. laevigatus and O. albidipennis, respectively. The lower thermal development threshold was significantly higher for O. albidipennis (14.2 +/- 0.9 degrees C) than for O. laevigatus (11.3 +/- 0.7 degrees C). No significant differences in fecundities between the two anthocorids were observed at 20, 25 and 30 degrees C. At 35 degrees C, O. albidipennis had a significantly higher fecundity than O. laevigatus. Non-linear models were used to explain reproduction and female survivorship in relation to temperature. The upper reproductive thresholds were estimated at 40.9 +/- 0.3 and 35.5 +/- 0.1 degrees C for O. albidipennis and O. laevigatus, respectively. The different optimum temperatures may explain, at least in part, the different distributions of the two species in the Palaeartic region and their population dynamics in greenhouses and natural vegetation in the south of Spain. The estimation of rm as a function of temperature showed high variability between years. Three release rates of 0.75-0.25 Orius per plant are recommended from early March to mid May to deal with thrips outbreaks in pepper crops.

Effects of Conventional Pesticides on the Preimaginal Developmental Stages and on Adults of Trichogramma cordubensis (Hymenoptera: Trichogrammatidae)

The effects of seven pesticides sprayed on hosts with parasitoids at different phases of egg to adult development (24, 24-48, 48-72, 72-96, 120-144, 192-216 h) of Trichogramma cordubensis (Vargas & Cabello) were studied. The effect of these pesticides on the mortality of adult parasitoids upon contact with the hosts immediately or 24 h after the treatments was also tested. One organophosphate insecticide (trichlorfon), one organochlorine insecticide (endosulfan), two pyrethroids (deltamethrin and lambda-cyhalothrin), a commercial formulation of Bacillus thuringiensis subsp. Kurstaki , and two fungicides (acetamide + dithiocarbamete and basic copper sulphate) were selected for testing. All the tests were carried out with fresh solutions of commercial insecticides applied on host eggs at the recommended concentration. The pesticides applied at different development phases did not affect the duration of parasitoid development, except endosulfan, which delayed the parasitoid preimaginal development for one day. With few exceptions, the number of parasitized host eggs that turned black (i.e. with parasitoid prepupae) did not differ significantly between the pesticide treatments and the control. The chemical insecticides affected the adult emergence rates significantly, while the other products resulted in emergence rates similar to control values. The longevity of adult progeny was very short when endosulfan or trichlorfon (<1 and <2 days, respectively) were applied. Overall, endosulfan was the pesticide most harmful to the preimaginal development stages of T. cordubensis . Therefore, the use of this product should be avoided when this species is part of an integrated pest control programme.

Avaliação da preferência de Bemisia argentifolii por diferentes espécies de plantas

Este trabalho teve como objetivo avaliar a preferência de Bemisia argentifolii em relação a algumas plantas hospedeiras potenciais como: abobrinha, feijão, repolho, tomate, mandioca, pepino, soja, pimentão, milho, poinsétia, brócolos e berinjela. Utilizou-se a metodologia de, em testes de livre escolha, expor uma população de mosca-branca previamente criada em plantas de poinsétia, às diversas espécies botânicas. Após 48h de exposição às diferentes espécies, insetos adultos e ovos presentes nas folhas foram contados e a área foliar medida, calculando-se o número de adultos e de ovos por cm² de área foliar. Em outro experimento, após três gerações de associação de uma população de mosca-branca com berinjela, repolho e mandioca, avaliou-se a utilização destas plantas como substrato para o desenvolvimento pré-imaginal de B. argentifolii. De maneira geral, as plantas abobrinha, tomate, feijão, pepino, berinjela, repolho e soja atraíram adultos de B. argentifolii, que efetuaram posturas nestas plantas. Mandioca, milho e pimentão foram as plantas menos preferidas. Uma relação positiva entre o número de adultos presentes, a área foliar e o número de posturas, sugere que o mecanismo de escolha do hospedeiro para alimentação e abrigo do adulto, envolve a conseqüente seleção do hospedeiro para oviposição. O número de adultos e ninfas foi maior em repolho e a porcentagem de ninfas vivas foi semelhante para repolho e berinjela. Em mandioca, uma elevada porcentagem de ninfas mortas demonstra não ser esta planta adequada para a sobrevivência do inseto.

Cold Storage of Coleomegilla maculata larvae

Short-term storage of second and third instars of the coccinellid Coleomegilla maculata lengi Timberlake can be achieved efficiently through utilization of temperatures below its thermal threshold of development. Survival, voracity and preimaginal development time were evaluated for larvae kept at 4 and 8°C for up to 5 weeks. Survival was close to 100% for the first two weeks of storage, but decreased drastically afterward and was 0% after 5 weeks. Storage at low temperatures did not diminish the voracity of larvae after storage. Development completely stopped during cold storage but resumed without significant effect after larvae were returned to 24°C. This study indicates for the first time that cold storage of C. maculata second and third instars is possible for a period of up to 2 weeks and provides a technique that could benefit biological control programs by increasing availability of beneficial insects.

Fecundity of Hoplopleura scapteromydis (Phthiraptera: Anoplura, Hoplopleuridae), ectoparasite of Scapteromys aquaticus (Rodentia: Muridae) in Rio de La Plata marshlands, Argentina.

Density and age structure of lice collected from captured Scapteromys aquaticus rodents were studied to estimate the fecundity of Hoplopleura scapteromydis. The number of eggs with a visible embryo inside (E), nymphs (N), adult males (AM), and adult females (AF) were recorded for each rodent. For the ith rodent, the fecundity of H. scapteromydis, F(i), was estimated as F(i) = [[E(i) + N(i)]/2]/AF(i)/T, where T represents the period of preimaginal development (unknown and arbitrarily considered as T = 1), and the sex ratio of the preimaginal stages was supposed to be 1:1. In order to look for density-dependent effects, F(i) was plotted against AM(i), this being an independent estimation of infrapopulation density. The number of rodents suitable for AF and AM calculations was 38 (57% of the parasitized animals). Almost 95% had a low-to-moderate louse burden (1 < AM < 30) and were captured every season, whereas only 3% had a heavy (61 < AM < 70, captured in winter) or very heavy (AM > 80, captured in summer) louse burden. The extreme values of F were 0.63 and 18 (1.3 and 36 if both sexes were considered). High-to-moderate F-values (F > 5) were estimated in only 5 rodents that exhibited low louse density, whereas low F-values (F < 5) were found at all louse densities. Notwithstanding the tendency toward an inverse relationship between fecundity and infrapopulation density, the correlation was not significantly different from 0.

Preimaginal Developmental Biology of Diachasmimorpha tryoni (Cameron), a Parasitoid of the Mediterranean Fruit Fly

The objectives of this study were to identify the preimaginal development of instars of Diachasmimorpha tryoni (Cameron) (Hymenoptera: Braconidae: Opiinae), a larvo-pupal parasitoid of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and to define its thermal requirements. Development was followed daily and parasitoid stage and size were noted. Larval samples were observed under a scanning electron microscope. Developmental rate as a function of temperature was studied with the Sharpe-DeMichele 6-parameter biophysical model and thermal requirements (lower developmental threshold and thermal constant) calculated using a linear regression. The duration of parasitoid development at seven temperatures ranged from 16.52 ± 0.96 days at 28 °C to 57.62 ± 1.85 days at 15 °C (males) and from 18.00 ± 0.79 days at 28 °C to 63.60 ± 1.52 days at 15 °C (females). Male development always took shorter than female development. No parasitoids emerged at 29 and 30 °C, which seems to be close to maximal temperature. The development required 322.6 ± 17.6 degree-days above a thermal threshold of 9.19 °C (both sexes cumulated). These data are compared with those of the host fruit fly, and the suitability of D. tryoni in controlling the Mediterranean fruit fly in Reunion Island is discussed.

Variation in Diapause Responses Between Geographic Populations of the Predator &lt;I&gt;Geocoris punctipes&lt;/I&gt; (Heteroptera: Geocoridae)

Abstract The effect of photoperiod on preimaginal development and diapause induction (for reproductive diapause) was evaluated for two geographic populations of the predator Geocoris punctipes (Say). One population was from Lexington, KY (N38° 04′, W84° 29′), and the other from Tifton, GA (N31° 28′, W83° 31′). Six photoperiods were used in the experiment (all at 24 ± 1°C): 10:14, 11:13, 12:12, 13:11, 14:10, and 15:9 (L:D) h. Photoperiod and population had significant effects on the developmental times of embryos and nymphs. However, the developmental differences had no apparent relationship with photoperiod, and those between populations were slight (<1 d). The incidence of diapause increased for both populations as photoperiod decreased, but at daylengths shorter than 14:10 (L:D) h, the frequency of diapause increased much more steeply in the Kentucky population than in the Georgia one. At its peak, the incidence of diapause in the Georgia population (40.9%; 10:14 [L:D] h) was about half that of the peak...

Effect of temperature on preimaginal development of Phyllocnistis Citrella Station on Kagzilime

Effect of temperature on preimaginal development of Phyllocnistis Citrella Station on Kagzilime

Photoperiodic control of the intensity of diapause and diapause development in the bean bug, Riptortus clavatus (Heteroptera: Alydidae)

Adult diapause in Riptortus clavatus (Thunberg) was induced by short-day photoperiods, and the critical daylength for its induction was 13.5 h. When insects were reared from eggs under diapause-inducing photoperiods near the critical daylength, the duration of diapause was shorter than when reared under the shorter daylengths. Adults terminated diapause under long-day photoperiods earlier when they had been raised under a near-critical photoperiod than under shorter daylengths; this indicated that the initial intensity of diapause was dependent on the length of the inducing photoperiod. Not only the photoperiods experienced during preimaginal development but also the value of the long-day photoperiods experienced after adult emergence affected the time of onset of oviposition. When the photophase was shortened, either abruptly or gradually after adult emergence, the duration of diapause was prolonged. Diapause was long when induced by shorter daylengths than the near-critical photoperiod. Different photoperiods have thus different quantitative effects on both the initial intensity of diapause and the rate of diapause development.

Effects of Prey on Survival, Development, and Reproduction of Trash-Carrying Chrysopids (Neuroptera:Ceraeochrysa)

Trash-carrying chrysopids within the genus Ceraeochrysa appear well-protected from intraguild predation, and several species show excellent potential for commercialization in the United States and Latin America. To facilitate their mass production and marketing, we evaluated how Ceraeochrysa cincta (Schneider), Ceraeochrysa cubana (Hagen), and Ceraeochrysa smithi (Navas) perform when larvae are reared on several different prey regimens, including two currently used to rear chrysopids commercially [eggs of the moths Anagasta kuehniella (Zeller) and Sitotroga cerealella (Olivier)]. All regimens that included the moth eggs gave substantially and significantly faster (by 3–4 d) preimaginal development and sometimes larger adults than did a diet of aphids [ Myzus persicae (Sulzer)]. Compared with S. cerealella, A. kuehniella eggs resulted in a slight (a1 d) but significant acceleration in larval development, but no effect on adult body size or reproductive traits. The prey regimens that we tested yielded no significant variation in either larval or imaginal survival; however, they affected the survival of the combined prepupal, pupal, and preemergent adult stages of C. cubana and C. smithi. Our results indicate that the three Ceraeochrysa species could be mass reared readily on either species of moth eggs ( A. kuehniella or S. cerealella ) commonly used as prey in the mass production of Chrysoperla. The findings also underscore that Ceraeochrysa is not restricted to homopteran prey.

Innate attraction supplants experience during host plant selection in an obligate plant-ant

In order to assess the relative contributions of innate attraction and environmentally-induced preference to nest plant selection by the obligate plant-ant Tetraponera aethiops, we submitted both mature and callow workers to paired choice tests using the leaves of four plant species, including their natural host plant Barteria fistulosa. Mature workers taken from nature as well as mature workers after 25 days of laboratory breeding (with or without contact with B. fifstulosa leaves) always showed a great preference for shelters made with the leaves of B. fistulosa. Similar results were obtained with callow workers isolated from any plant material during the first 25 days of imaginal (=adult) life or during pre-imaginal development. But those reared in contact with test-plant leaves for the same two periods showed significantly less preference for B. fistulosa than did the controls. As a result, experience gained during the larval and nymphal stages as well as during the first part of adult life (i.e. pre-imaginal as well as early learning) was demonstrated in T. aethiops, but in this situation of species-specific interaction it reinforces innate attraction as both larvae and adults live in contact with B. fistulosa in nature. These results are discussed in comparison with previous data collected on arboreal ants not specifically paired with a plant, for which an environmentally-induced preference can supplant innate attraction.

Temperature-Dependent Effects on Development, Mortality, and Growth ofHippodamia convergens(Coleoptera: Coccinellidae)

Insect natural enemies selected for specific traits such as faster developmental times, higher survivorship, increased fecundity, and larger body size might be considered during production of biological control agents in certain situations. For instance, traits related to developmental rates may be selected for if genetically based variation exists within temperature-dependent responses. We compared preimaginal development, mortality, and size of Hippodamia convergens Guerin-Meneville at 4 constant temperatures (18, 22, 26, and 30°C). Total preimaginal development ranged from 51 d at 18°C to 14 d at 30°C. Developmental times were significantly different among isofemale lines of field-collected H. convergens from Oregon at all temperatures tested (18, 22, 26, and 30°C). Variation within female lines was significant only at 26°C. The lower developmental thresholds for egg, larval, and pupal stages were 9.9, 13.7, and 14.5°C, respectively. Degree-day (DD) requirements for development were 58.8, 166.7, and 52.6 for eggs, larvae, and pupae, respectively. Total preimaginal development required 231 DD above a temperature threshold of 13.6°C. Degree-day requirements for 14 field-collected female lines varied from 223 to 273, whereas the lower threshold for development ranged from 13.1 to 13.8°C. Mortality decreased with increasing temperatures. At the lower temperature (18°C), higher mortality occurred during the 4th instar and pupa. Pupal and adult weights differed across temperatures. Heavier pupae and adult beetles were reared at 22°C. Also, wings were larger among beetles reared at 22°C. The development, mortality, and size measurements provide data for establishing suitable rearing conditions for future studies on the ecology of H. convergens.