Developmental Threshold Temperature Research Articles

A Mechanism for the Decrease in Developmental Period of a Trivoltine Population of Hyphantria cunea (Lepidoptera: Arctiidae)

The life cycle of the fall webworm, Hyphantria cunea, has differentiated from bivoltine to trivoltine since the early 1970's in the southwestern areas of Japan. Previous studies showed differentiation in developmental period as well: development was shorter in the trivoltine populations. In the present study, the precise mechanisms of this change were investigated by comparing developmental characteristics between bivoltine (Akita) and trivoltine (Urawa) populations. The theoretical lower threshold temperatures for larval and pupal development were not different between the two populations. The thermal constant for larval development was smaller in the trivoltine population than in the bivoltine population, but that for pupal development was almost identical for the two populations. Most individuals passed six larval instars, and some passed seven in both populations. The incidence of seven-instar larvae was significantly higher in the bivoltine population than in the trivoltine population. The larval period was significantly longer in the seven-instar type than in the six-instar type. Larvae of the six-instar type grew at similar rates in the two populations. Head width of last instar larvae was larger in the seven-instar type than in the six-instar type, but pupal weight was not statistically different between the two types. These results suggest that the reduction in developmental period in the trivoltine population can be attributed to a reduction in the thermal constant, especially than during the larval stage. A lower incidence of seven-instar larvae appears to be the major mechanism for reducing the thermal constant in the trivoltine population.

Development of eggs of dragonflies (Odonata: Anisoptera) from two streams in north‐eastern Victoria, Australia

The development of the eggs of six species of Anisoptera from the Kiewa River and Middle Creek, Victoria was studied by incubating eggs over a range of temperatures, comparable to that found in the two streams. The eggs of each species developed directly, with an increase in development rate with increase in temperature. There appeared to be differences in the lower developmental threshold temperatures of coexisting species of Gomphidae and Libel‐Iulidae.

The temperature threshold for development of Elaphostrongylus rangiferi in the intermediate host: an adaptation to winter survival?

To test the hypothesis that the relatively high developmental temperature threshold of the parasitic nematode Elaphostrongylus rangiferi in the intermediate snail host is an adaptation to minimize larval mortality during winter, an experiment was set up in which snails of the species Arianta arbustorum were experimentally infected with the parasite. The snails were divided into 3 groups known to contain 1st, 2nd or 3rd-stage larvae, and incubated at 3 degrees C for an experimental period of 18 weeks. First-stage larvae showed a significantly higher survival rate within snails than 2nd or 3rd-stage larvae. We also found that snails carrying 1st-stage larvae survived better than snails with other larval stages. It is concluded that if the nematode has started development before the hibernation, this has a real and significant effect on the risk of dying. The high developmental threshold is therefore likely to be an adaptation to reduce the chance of hibernating as developing larvae during long periods of low temperatures.

Survival and Development of Ixodes scapularis (Acari: Ixodidae) Under Various Climatic Conditions in Ontario, Canada

Distribution of the blacklegged tick, Ixodes scapularis Say, is poorly defined in Ontario. An endemic population is known on Long Point peninsula, Lake Erie, Ontario, but I. scapularis adults have also been collected from other localities within the province. To test the hypothesis that distribution of the blacklegged tick is limited by cold climatic extremes, 35 fed female, 70 unfed adult, and 70 unfed nymphal I. scapularis were held in containers within four natural habitats on Long Point (42 degrees 36' N; 80 degrees 5' W) and at northern localities near Ottawa (45 degrees 27' N; 75 degrees 42' W), Hearst (49 degrees 40' N; 83 degrees 41' W), and Kenora (49 degrees 47' N; 94 degrees 29' W), Ontario, from early December 1991 until May 1993. At the northern localities, 84.8 and 30.5% of fed females and unfed adults survived overwinter, respectively. On Long Point, 56.4% of fed females and 23.6% of unfed adults successfully overwintered. Longevity of fed females and unfed adults was increased by > 2 mo at the northern localities compared with Long Point, although survival rates for unfed nymphs at the northern sites and on Long Point were similar. Females within the four habitats on Long Point, and at Kenora and Ottawa, laid eggs from late April to mid-May, whereas eggs were deposited in late June at Hearst. Emergence of larvae from eggs began in late July or early August on Long Point and at Ottawa. Larvae were first observed in early October at Kenora, and no larvae emerged during 1992 at Hearst. Some eggs that overwintered during 1992-1993 at the northern sites were viable; however, hatching rate was < 10%. The minimum duration of the life cycle of I. scapularis is extended when ticks are introduced into regions of the province with seasonal degree-day accumulations lower than those observed on Long Point. Delays in deposition of eggs and emergence of larvae at Hearst and Kenora were likely a result of insufficient accumulation of degree-days above threshold temperatures for development in 1992. Though some eggs can overwinter successfully, suggesting that latitude-related reduction in seasonal temperature may not limit distribution of this tick in Ontario, hatchability was low. This factor, combined with innate incremental mortality at each instar, difficulty in finding a mate, and low density of medium to large mammal hosts for adults, may mitigate against establishment of I. scapularis by introduction of individual ticks into certain northern regions.

Influence of Temperature On the Development and Survival of Meloidogyne Javanica

Responses to temperature of a population of Meloidogyne javanica from Tanzania were examined. The minimum time for development from J2 to first J2 of the next generation was determined over a temperature range from 18-30°C. The rate of development increased linearly between 18°C and 27°C and, on a thermal time basis, the threshold or base temperature for development was estimated by extrapolation to be 12.9° C and the requirement for development c. 350°C days above base. These values are compared with those for M. hapla, a temperate species, and their effects on development time in relation to temperature are discussed. The effect of higher temperatures on egg viability was also tested. Short exposures to 70°C were lethal and exposure to 45°C and above killed a progressively increasing proportion of eggs. Exposure in the field in Tanzania of egg masses buried at different depths to solarization under clear polythene sheeting showed that at 15 cm depth all eggs were dead after 2-3 weeks with an average and a maximum soil temperature at 16.00 h of 43°C and 45°C respectively for the covered and 40°C and 42°C for the uncovered plots. Irrigating the plots before covering slightly decreased mean soil temperatures compared with the covered, dry plots and greatly increased egg survival.

Development Rate and Mortality of Immature Parasarcophaga (Liopygia) ruficornis (Diptera: Sarcophagidae) at Constant Laboratory Temperatures

Developmental time of Parasarcophaga ruficornis (F.) was determined at constant temperatures of 13, 16, 19, 22, 25, 28, 31, 34, and 37 degrees C. Estimates of the lower developmental threshold temperatures (tL) were 10.5, -7.0, 6.3, 8.8, and 7.7 degrees C and the thermal constants (K) were 65.15, 111.93, 152.13, 229.66, and 388.22 degree-days (DD) for feeding larvae, wandering larvae, larvae (feeding + wandering), pupae, and total developmental time, respectively. Flies reached their maximum weight in pupal and adult stages at 25 and 28 degrees C, whereas minimal weights were recorded at 16 and 37 degrees C. The optimal temperature in terms of rapid development, low mortality, and greatest weight ranged between 22 and 28 degrees C.

Development and fecundity of Sesamia calamistis (Lepidoptera: Noctuidae) and Eldana saccharina (Lepidoptera: Pyralidae)

AbstractThe developmental rates and fecundity of two important African maize pests, Sesamia calamistis Hampson and Eldana saccharina Walker, were studied under constant temperatures and with two larval diets. Five temperatures (15°, 20°, 25°, 30° and 35°C) were used to investigate developmental rates and three temperatures (20°, 25° and 30°C) were used in fecundity experiments. Larvae were reared on maize stem cuttings and on artificial diet. The developmental period for S. calamistis on artificial diet required over 700 degree-days (DD); eggs needed 122 DD above a threshold of 9.7°, larvae required 383 DD above 12.2°C and pupae 204 DD above 10.2°C. The developmental period for E. saccharina on artificial diet was 665 DD; eggs required 125 DD above 9.1°C, larvae 400 DD above 10.6°C and pupae 140 DD above 8.8°C. On artificial diet both species developed faster and had higher threshold temperatures for larval development than when reared on maize stem cuttings. Pupal development rates did not differ between artificial diet and maize stem for either species, although developmental thresholds were marginally lower on artificial diet. S. calamistis averaged 250–690 eggs/female although some individuals produced more than 1000 eggs. Adult females lived 5.7 days at 30°C and 10 days at 20°C. E. saccharina females produce more eggs and lived longer than S. calamistis females. Average fecundity for E. saccharina was 470–620 eggs/female, but several individuals produced more than 1200 eggs. Adult females lived 6.6 days at 30°C and 14.6 days at 20°C.

Biology ofTetrastichus howardi(Olliff) (Hymenoptera: Eulophidae): A facultative Hyperparasitoid of stem borers

The biology of the parasitoid Tetrastichus howardi, which was introduced from the Philippines into South Africa for the biological control of the stem borer Chilo partellus, was studied in the laboratory. On average, a T. howardi female produced 101 progeny (92% females) which developed in 4.3 hosts. The upper threshold temperature for development was around 33°C, the minimum threshold was calculated as 12.8°C and the thermal constant as 239.8 day‐degrees. With hosts, females lived 23.6 and males 16.7 days. T. howardi was found to be a facultative hyperparasitoid with a very wide host range. As a primary parasitoid, it developed in pupae of various Lepidoptera as well as Coleoptera and Hymenoptera and as a hyperparasitoid in dipteran and hymenopteran parasitoids. A linear relation was found between the number of emergent parasitoids and the volume of the host from which they emerged. Preference tests indicated that T. howardi preferred to parasitize the phytophagous insects C. partellus and Heliothis armi...

Egg Development in Hexagenia limbata (Ephemeroptera:Ephemeridae) from Southern Indian Lake, Manitoba: Temperature Effects and Diapause

Egg development was investigated for Hexagenia limbata (Serville) from Southern Indian Lake (SIL) in northern Manitoba, Canada. The SIL population is located near the northern range limit of H. limbata, and some important differences in hatching dynamics were seen in comparison with southern populations. Hatching success and egg development time were related to temperature, as reported in the south, but the developmental threshold temperature for the SIL population was near 8°C, 2° lower than previously reported. Storage of the eggs at 8°C resulted in slow but measurable development rather than low-temperature quiescence as expected, leading to inconsistent degree-day estimation among temperature treatments. Following storage at 8°C, both egg development rate and hatching success increased with increasing temperature. However, hatching success was improved by increasing the time the eggs spent in storage, ranging from only 50% hatch in unstored eggs to >90% hatch in eggs stored for ∼6 mo. In addition, a bimodal hatching response was seen in the eggs; about half of the eggs deposited by individual females hatched immediately under favourable conditions, and the remainder hatched after exposure to cold (4°C). A lower developmental threshold than previously reported and a previously undescribed egg diapause may enable Hexagenia limbata to persist near the northern extent of its distribution.

DEVELOPMENT AND SURVIVAL OF PODISUS MACULIVENTRIS (SAY) AND PODISUS SAGITTA (FAB.) (HETEROPTERA: PENTATOMIDAE) AT VARIOUS CONSTANT TEMPERATURES

AbstractDevelopment and survival of the predatory pentatomids Podisus maculiventris (Say) and Podisus sagitta (Fab.) were studied at six constant temperatures ranging from 19 to 35 °C. Time required for development from egg to adult ranged from 48.9 days (19 °C) to 18.9 days (30 °C) for P. maculiventris and from 51.9 days (19 °C) to 16.9 days (33 °C) for P. sagitta. At 33 °C, eggs of P. maculiventris did not hatch and development of nymphs that had emerged at 23 °C was retarded; none of the first-instar nymphs incubated at 35 °C survived the next moult. A constant temperature of 35 °C was fatal to P. sagitta eggs and extended the developmental period of nymphs from 23 °C. Egg hatch ranged from 47% (19 °C) to 57% (27 °C) for P. maculiventris and from 54% (33 °C) to 71% (27 °C) for P. sagitta. Nymphal survival was high at moderate temperatures, with 63–78% and 65–82% of the first-instar nymphs of the respective species reaching adulthood. Mortality during the nymphal stage was significantly increased at high temperatures, but was considerably lower for P. sagitta than for P. maculiventris. Lower threshold temperatures for egg and nymphal development were estimated to be 10.7 and 11.7 °C for P. maculiventris, and 13.3 and 12.2 °C for P. sagitta. Thermal requirements for these stages were 78.2 and 275.5 degree-days, and 60.9 and 265.5 degree-days, respectively. These observations suggest that P. sagitta is somewhat better adapted to high temperatures than is P. maculiventris.

Effect of Temperature on the Egg Hatching of Potamanthus formosus (Ephemeroptera: Potamanthidae).

Eggs of Potamanthus formosus were kept at constant temperature (range 4.8-30°C) in the laboratory. The percentage of eggs hatched was 34-53% over a mean temperature range of 15-30°C, peaking at ca. 20°C, but dropping abruptly below 15°C to almost zero at ca. 13°C. The developmental time (Y) was inversely related to the water temperature, and the relationship was well described by a hyperbolic equation. The threshold temperature for egg development was calculated to be 10.5°C for 50% hatch based on the relationship between the rate of development (1/Y) and temperature. This suggests that the threshold temperature for egg development may differ from that for egg hatching. The calculated values of the summation of effective degree-days were 222.2 above 10.5°C for 50% hatch. Extrapolating the results to a natural stream, eggs must be laid until late in September to hatch by the time water temperature decreases to 15°C. The above estimation suggests that eggs laid late in the emergence period from June to October would not hatch before winter. These eggs may overwinter and hatch in spring. This conjecture is supported by the fact that the number of tiny nymphs evidently increased in April and May.

The Phenology of the Native Dung Beetle Onthophagus-Australis (Guerin) (Coleoptera, Scarabaeinae) in South-Eastern Australia

Onthophagus australis (Guerin) is predominantly univoltine at two sites in south-eastern Australia, with Peaks Of activity in spring when most oviposition takes place, and in autumn when the new generation emerges. It overwinters mainly in the adult stage, and populations decline during summer droughts. The optimum temperature for oviposition is between 20 and 25-degrees-C, and the beetle produces food balls intermittently throughout life. The threshold temperature for development was estimated to be 5.2-degrees-C, and 1612 day-degrees (degrees-C) are required for development from egg to adult. In the laboratory, 100 beetles in a 1-L dung pad are able to reduce bush fly survival by 74%, and reduce the size of the fly puparia by 18%. In spring, when bush flies first build up their populations in the field, numbers of 0. australis did not often reach 100 per pad, thus limiting their usefulness for the biological control of the bush fly.

A TEMPERATURE-DEPENDENT MODEL OF EGG DEVELOPMENT OF THE WESTERN CORN ROOTWORM, DIABROTICA VIRGIFERA VIRGIFERA LECONTE (COLEOPTERA: CHRYSOMELIDAE)

AbstractDevelopmental rates of post-diapause eggs of Diabrotica virgifera virgifera LeConte were compared in the laboratory at six constant temperatures, 12, 16, 20, 24, 28, and 32°C. Linear and nonlinear models were fitted to temperature versus developmental data and were used to predict egg hatch in the field. A four-parameter model fitted to median developmental rates (r2 = 0.99) indicated that development was linear between 16 and 28°C, optimal at 28°C, and decreased at 32°C. The lower development threshold (± SE) (10.5 ± 0.1°C) was determined by linear regression and the x-intercept method. Completion of post-diapause egg development required 258 ± 3 degree-days (± SE) above the base temperature. This compared well with the mean degree-days accumulated to 50% hatch (± SE) of 265 ± 24 which we observed in the field at several locations over 3 years using a degree-day model incorporating an 11°C developmental threshold and soil temperatures at 5- and 10-cm depths. A stochastic simulation model, incorporating a nonlinear developmental function dependant on soil temperatures taken every 2 h also predicted 50% hatch within 2 days. This model was validated in the field with 19 independent records of soil temperatures for several locations at two depths in the soil over 3 years. The simulation model accurately predicted time of 5 and 95% hatch, which indicates that this model has broad application in predicting the pattern of egg hatch for pest management.

Factors Facilitating the Continued Presence of Colotis evagore (Klug, 1829) in Southern Spain

Colotis evagore (Klug) is a multivoltine pierid butterfly that has repeatedly invaded the Iberian Peninsula from Africa over the last four decades. In 1983 it invaded Spain, reproducing successfully there on its foodplant, Capparis spinosa L. During the cold season this plant is not available in most areas of Spain, and the butterfly must find alternative foodplants to maintain its populations in this newly colonized territory. Our data show that C. evagore is unable to survive on alternative cruciferous hosts, and incapable of entering diapause to avoid inhospitable times of the year and the absence of host plants. The relative growth rate of larvae depends on temperature; the threshold temperature for development is 12?C, and the estimated physiological time for larval development is 162.5?d. Our observations show that C. evagore has survived continually in certain coastal sites in southern Spain since 1983. Microenvironmental conditions in these sites are particularly favourable for the foodplant. Hence, the plant is available throughout the year, allowing the caterpillars to complete successfully their life-cycle.

Similarities in Developmental Rates of Geographically Separate European Corn Borer (Lepidoptera: Pyralidae) Populations

Developmental velocities of European corn borer, Ostrinia nubilalis (Hubner), colonies collected at four geographically separate locations (Delaware, Iowa, Missouri, and North Dakota) were compared. Each colony was reared under five or six constant temperature regimes. Mean developmental times and standard deviations about the means were determined. Developmental velocities were used to formulate both linear and sigmoid developmental velocity equations. Because the sigmoid and linear functions exhibited similar fits to the data, the latter were used in a European corn borer phenology model that predicts the period of second generation oviposition. The resulting predicted oviposition periods are reported for model runs using developmental velocity equations generated for the four colonies. The resulting predictions suggest that developmental rates are similar among the four geographically separate European corn borer populations. For European corn borers reared at 32°C, however, developmental times and developmental threshold temperatures during the period of larval eclosion to adult emergence appeared different among the colonies.

Temperature-Dependent Development and Phenology of Pepper Maggots (Diptera: Tephritidae) Associated with Pepper and Horsenettle

Emergence and developmental rates of nondiapausing pepper maggot, Zonosemata electa (Say), pupae, reared from naturally infested pepper ( Capsicum annuum L.) and horsenettle ( Solanum carolinense L.) fruit, were compared at seven constant temperatures: 5, 10, 15, 20, 25, 30, and 35°C. Pupae originating from pepper had significantly greater pupal weights and percentage of adult emergence than pupae from horsenettle. However, host plant origin, color, sex, and weight had little influence on pupal developmental times across temperatures. Nonlinear and linear models were fit to the temperature versus developmental data and used to predict adult emergence in the field. A nonlinear, four-parameter, poikilotherm model, fitted ( r2 = 0.99) to median development rates of pepper and horsenettle pupae combined, indicated that development was linear between 10 and 25°C, optimal at 26°C, and dropped to near zero at 35°C. The lower developmental threshold (± SE) for horsenettle- and pepper-reared pupae combined (9.33 ± 0.09°C)was determined by linear regression and the x intercept method. Completion of pupal development for the combined sample required 602 ± 13 degree-days (±SE) above the base temperature. Contrary to previous reports, phenology of adult pepper maggot in the field was unaffected by host plant origin. A degree-day model incorporating a 9.5°C developmental threshold and soil temperatures (10 cm depth) accurately predicted (±l d) the 50% emergence points (E 50 ) of adults reared from both host plants. A stochastic simulation model, incorporating a nonlinear developmental rate function and 2-h soil temperature records, also predicted the E 50 point accurately (±1.5 d). The simulation model accurately predicted the E 5 and E 75 to E 100 points, making it useful in management situations where emergence percentiles other than 50% are required.

Influence of Temperature and Plant Growth Stage on Development, Reproduction, Life Span, and Intrinsic Rate of Increase of the Russian Wheat Aphid (Homoptera: Aphididae)

Plant growth stage and temperature exhibited a significant interaction ( P < 0.05) in their effects on reproductive life span, total life span, and production of nymphs per female of Russian wheat aphid, Diuraphis noxia (Mordvilko). Immature development and daily fecundity were not significantly affected by temperature and growth stage interactions. Minimum threshold temperature for immature development was estimated to be −1.57°C, and the number of degree-days to complete preimaginal development was 225.57. The intrinsic rate of increase (rm) was highest (0.255 ± 0.005) at 18–21°C during the jointing stage of wheat. At all other growth stages except tillering, rm also was highest at 18–21°C. Wheat growth stages from jointing to heading and a temperature regime of 18–21°C seem to be most suitable for rearing Russian wheat aphids in the laboratory, considering aphid fecundity and plant tolerance to insect and temperature stress.

Survival and Development of the Immature Stages of Culex annulirostris (Diptera: Culicidae) at the Ross River Dam in Tropical Eastern Australia

Immature stages of Culex annulirostris Skuse from Ross River Dam were reared in the laboratory at constant temperatures (18.0, 24.5, 28.5 and 35.0 degrees C) and in the field in the presence or absence of predators. In the laboratory, survival from first instar to adult emergence increased from 5.5% at 18 degrees C to 96.5% at 35 degrees C. In the field predators increased mortality by almost 60%. Adult wing length increased inversely with constant temperature except at 18 degrees C. In the field the largest adults were produced in the presence of predators. The developmental threshold temperature (to) and thermal constant (K) were estimated from laboratory data to be 13.7 degrees C and 129.3 DD, respectively. K determined in the laboratory did not differ significantly from that required in the field (132.8 and 153.5 DD above 13.7 degrees C in the presence and absence of predators). Numbers of immature Cx. annulirostris at four sites in the dam rose to a peak after four or five generations and then rapidly declined. Overall survival of immatures was very low but was significantly higher at the one site where Melaleucas also occurred. Age-specific survival was highest in the first instar. Estimated survival from hatching to eclosion ranged from 4/1,000 to 185/1,000. Mortality appeared to be density independent and was attributed mostly to predation.

Biology of Anagrus delicatus (Hymenoptera: Mymaridae), an Egg Parasitoid of Prokelisia marginata (Homoptera: Delphacidae)

Anagrus delicatus Dozier is a common egg parasitoid of the planthopper Prokelisia marginata (Van Duzee). P. marginata inhabits salt marshes along the Atlantic and Gulf Coasts of the United States and feeds exclusively on salt marsh cordgrass, Spartina alterniflora Loisel. A. delicatus is closely associated with its host throughout its range. Two larval instars of A. delicatus were identified from their host eggs. Male and female wasps take an average of 54.2, 35.9, and 21.7 d to develop from egg to adult at 16, 22, and 30°C, respectively. The developmental threshold temperature is approximately 7.1°C, and wasps require a minimum of 504 degree-days (DD) to complete development. The sex ratio of emerging adults is skewed toward females (1:2.4, M/F). Females eclose with an average of 33 eggs (range, 21-46) and are capable of immediate mating and oviposition. Females can produce male offspring parthenogenetically, and virgin females parasitize significantly more hosts during the first 24 h than mated females. Life for adult females was relatively short: females fed honey and water lived an average of 3.3 d, but those provided only water averaged just 2.0 d. Females laid 25% of their eggs on the first day, and oviposition ceased by the third day. In all, oviposition for honey-fed females ceased after only 43% of the eggs were laid. Host eggs are capable of being parasitized throughout development, but parasitoid survival in older host eggs (embryos) is lower than in younger eggs.

Threshold Temperatures and Thermal Requirements for the Development of Spodoptera litura (Lepidoptera: Noctuidae)

Developmental thresholds and thermal requirements for different stages of Spodoptera litura (F.) fed on groundnut leaves were determined under constant laboratory conditions and in the field. An average of 64 degree-days (DD) above a threshold of 8°C was required from oviposition to egg hatch; the larval period required 303 DD and pupal stage 155 DD above a 10°C threshold; females needed 29 DD above a 10.8°C threshold from emergence to oviposition. Fifth and sixth instars accounted for about 50%of the total larval requirement under laboratory and field conditions. The response of various stages of S. litura to temperatures under constant laboratory conditions was similar to that under field conditions. The upper developmental threshold temperature of all stages was 37°C; 40°C was lethal.