Effects of Temperature on Development and Survival of Nymphal Lycorma delicatula (Hemiptera: Fulgoridae)

Lycorma delicatula (White), an invasive planthopper originally from Asia, is an emerging pest in North America. It is important to understand its phenology in order to determine its potential range in the United States. Lycorma delicatula nymphs were reared on Ailanthus altissima (Miller) (Sapindales: Simaroubaceae) at each of the following constant temperatures: 5, 10, 15, 20, 25, 30, 35, and 40°C. The time spent in each instar and survival was recorded. Developmental rate increased with temperature from 15 to 30°C for all instars, then declined again at higher temperatures. Nymphal survival was lower at 35°C than between 15 and 30°C for all instars, and first instars placed at 5, 10, and 40°C all died without molting. This suggests that L. delicatula survival and development may be affected in the Southern United States by high temperatures and developmental delays will occur under cool spring conditions. The lower developmental threshold was found to be 13.00 ± 0.42°C for first instars, 12.43 ± 2.09°C for second instars, 8.48 ± 2.99°C for third instars, and 6.29 ± 2.12°C for fourth instars. The degree-day (DD) requirement for nymphs in the previous instar to complete development to reach the second instar, third instar, fourth instar, and adult was 166.61, 208.75, 410.49, and 620.07 DD (base varied), respectively. These results provide key data to support the development of phenology models and help identify the potential range of L. delicatula in North America.

Development of Hydrotaea spinigera (Diptera: Muscidae) at Constant Temperatures and Its Significance for Estimating Postmortem Interval

Hydrotaea spinigera Stein is a necrophagous species, widely distributed in Oriental and Australasian regions. Considering that the postfeeding larvae or puparia of this species can still be found in abundance at the advanced decomposition stage or even the skeleton stage of remains, it can serve as a good supplementary indicator for estimating the minimum postmortem interval (PMImin). This could also extend the range of PMImin when the primary colonizers are no longer associated with the corpse or have emerged as adults. This study investigated the development duration, accumulated degree hours, and larval body length changes of H. spinigera at seven constant temperatures ranging from 16 to 34°C, and established three development models for estimating PMImin, including isomorphen diagram, isomegalen diagram, and thermal summation model. At 16, 19, 22, 25, 28, 31, and 34°C, the development durations of H. spinigera from egg to adult stage were 1,412.6 ± 62.9, 867.4 ± 14.9, 657.1 ± 22.9, 532.3 ± 10.1, 418.8 ± 21.3, 379.8 ± 16.6, and 340.0 ± 20.3 h, respectively. The lower developmental threshold L0 was estimated as 10.50 ± 0.20°C, and the thermal summation constant K was 7,648.83 ± 146.74 degree hours. Using regression analysis, equations were obtained modeling the change of larval body length with time after hatching at different temperatures. This study provided basic data based on the growth and development of H. spinigera for the estimation of PMImin in forensic science.

Herbivore Larval Development at Low Springtime Temperatures: The Importance of Short Periods of Heating in the Field

Temperature has been shown to play an important role in the life cycles of insects. Early season feeders in Palaearctic regions profit by the high nutritional quality of their host plants early in the year, but face the problem of having to develop at low average springtime temperatures. This study examines the influence of short periods of heating in the field on larval development and on mortality with the model systemGaleruca tanacetiL. (Coleoptera: Chrysomelidae), an early season feeder, that hatches at low springtime temperatures. Field and laboratory experiments under different constant and variable temperature regimes were performed. While in the field, the average daily temperature was close to the lower developmental threshold of the species of 10.9°C; maximum temperatures of above 30°C were sometimes reached. Larvae developed significantly faster, and pupae were heavier, in the field and in an assay with short periods of heating than at the same average temperature under constant conditions in the laboratory. We conclude that larvae profit substantially from short periods of heating and temperature variation in the field and that intervals of high temperature enable insect survival and exploitation of nutrient-rich food resources at early times in the season.

Biological and ecological traits that assist establishment of alien invasive insects

In this study the biological and ecological traits of two groups of phytophagous insect pests were examined to determine attributes that may influence establishment in New Zealand Biological and ecological attributes of a group of insect species that is established in New Zealand were compared with species that are not currently established It was found that the species established in New Zealand had a significantly wider host plant range than species that have not established The lower developmental threshold temperature was on average 4C lower for established species compared with nonestablished species These data suggest that species that establish well in New Zealand have a wide host range and can tolerate lower temperatures compared with those that have not established

Survival and development of different life stages of three Ceratitis spp. (Diptera: Tephritidae) reared at five constant temperatures

Fruit flies (Diptera: Tephritidae) are the most damaging pests on fruit crops on Réunion Island, near Madagascar. Survival and development of the Mediterranean fruit fly, Ceratitiscapitata (Wiedemann), the Natal fruit fly, C. rosa Karsch and the Mascarenes fruit fly, C. catoirii Guérin-Mèneville were compared at five constant temperatures spanning 15 to 35°C. Durations of the immature stages of C. capitata, C. rosa and C catoirii ranged from 14.5–63.8, 18.8–65.7 and 16.8–65.8 days, respectively, at 30–15°C. The lower developmental threshold and thermal constant were calculated using the temperature summation model. The thermal constant for total development of the immature stages of C. capitata, C. rosa and C. catoirii were 260, 405 and 356 DD, respectively. Species differed mainly during the larval stages and ovarian maturation period, with smaller differences in the egg stage. Ceratitis rosa appeared to be better adapted to low temperatures than the two other species as it showed a lower larval developmental threshold of 3.1°C compared to 10.2°C for C. capitata and 8.9°C for C. catoirii. Overall, C. catoirii had a low survival rate within the range of temperatures studied. The different responses of the three Ceratitis species to various temperatures explain to some extent their distribution on the island. The results obtained will be used for optimizing laboratory rearing procedures and for constructing computer simulation models to predict fruit fly population dynamics.

Seasonal trends in the rate of population increase of Frankliniella occidentalis (Thysanoptera: Thripidae) on cucumber

The developmental rate of Frankliniella occidentalis (Pergande) was determined on cucumber Cucumis sativus cv. Sandra over a range of constant temperatures. The lower developmental threshold (LDT) and the sum of effective temperatures (SET) for the pre-imaginal development were 10.7°C and 231.1°C, respectively. The rate of population increase was assessed as the sum of effective temperatures above the lower developmental threshold by monitoring the numbers of thrips on individual leaves of cucumber under commercial greenhouse conditions. Population growth was characterized by an early stochastic phase, corresponding to pre-imaginal development of the first generation, and followed by an exponential phase starting with the second generation, the rate of which did not vary between plants. Throughout the exponential phase, the rate of population growth increased with time/age of plant. As significant damage to cucumber may occur during the exponential phase of population increase, the sum of effective temperatures of 231°C can be used to predict when damage is likely to start to occur.

THERMAL CONSTANTS FOR PREIMAGINAL DEVELOPMENT OF THE PARASITOID CEPHALONOMIA STEPHANODERIS BETREM (HYMENOPTERA: BETHYLEDAE)

The relationship between temperature and rate of development is described for Cephalonomia stephanoderis Betrem, an imported ectoparasitoid of the coffee berry borer Hypothenemus hampei (Ferrari).For all stages, development rate increased linearly with temperature between 17 and 32°C. However, at 37°C both eggs and larvae died. When the parasitoid constructed a cocoon, the lower developmental threshold (t) varied from 11.8°C in the eggs to 14.2°C for pupae; when no cocoon was constructed, it varied from 11.8°C for the eggs to 14.3°C for pupae. The lower developmental threshold, from egg to adult, was 13.7°C (with cocoon) and 13.8°C (without cocoon). As these differences were small in relation to the standard errors of the estimates, they were not considered different. Because C. stephanoderis always constructs a cocoon under field conditions, the threshold temperature of 13.7°C seems to be the most suitable.Physiological time expressed in degree-days (DD) for the egg to adult cycle of C. stephanoderis is 252.7 ± 45.3 DD (α = 0.05) when a cocoon is constructed, and 242.5 ± 35.1 DD (α = 0.05) when pupation occurs without construction of a cocoon.

DEVELOPMENTAL TIME AND HOST SELECTION BY THE APHID PARASITOID APHELINUS SP. NR. VARIPES (FOERSTER) (HYMENOPTERA: APHELINIDAE)

Developmental rates, lower developmental threshold, host selection among three species of aphid, and head capsule width were determined for the parasitoid Aphelinus sp. nr. varipes (Foerster) (Hymenoptera: Aphelinidae). Aphid species used were Russian wheat aphid, Diuraphis noxia (Mordvilko), western wheat aphid, Diuraphis tritici (Gillette), and corn leaf aphid, Rhopalosiphum maidis Fitch. Developmental rate was determined at five constant temperatures, 11.3, 14.7, 19.0, 25.7, and 30.3°C. Developmental times of the wasp were similar in Russian and western wheal aphids, ranging from 88.7 days al 11,3°C to 11.3 days at 30.3°C. Lower developmental threshold was similar in both species, 9.7°C in Russian wheat aphid and 9.4°C in western wheat aphid. Because of the low number of corn leaf aphid s parasitized, it was not possible to compute a parasitoid development threshold in that host. In the host selection test, there were no significant differences in numbers of Russian and western wheat aphids attacked; corn leaf aphid was seldom attacked. The western wheat aphid is a native species that also causes leaf-rolling; we believe it was the primary host of the parasitoid before the arrival of the Russian wheat aphid. Wasps emerging from Russian wheat aphid were consistently larger than those emerging from western wheat aphid. Mean head capsule width for 30 female wasps from Russian wheat aphid was 0.33 mm; from 30 female wasps from western wheat aphid mean head capsule width was 0.20 mm.