Differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail,Papilio machaon (Lepidoptera: Papilionidae), from the Osaka population

To clarify differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail, Papilio machaon, we reared larvae from the Osaka population under photoperiods of 16 h light : 8 h dark (LD 16:8) (long day) or LD 12:12 (short day) at 20°C. We examined the relationship between food consumption and weight during the final larval stadium and pupae, and measured the pupal supercooling point (SCP). Although the ratio of assimilation to consumption did not differ significantly between photoperiods, the ratio of assimilation to pupal weight differed significantly between individuals reared under long and short days. All diapausing pupae were brown, whereas 56% of non‐diapausing pupae were green with the remainder brown. The mean pupal body length (L), dorsal width (W₁) and lateral width (W₂) were larger in non‐diapausing than in diapausing pupae, and the W₁/L and W₁/W₂ ratios differed significantly between non‐diapausing and diapausing pupae. SCP was approximately –20°C and did not differ among pupae 5, 15 and 30 days after pupation under long‐day conditions. However, under short‐day conditions, mean SCP gradually decreased, stabilizing at approximately –24 to –25°C by 30 days after pupation. After freezing, some diapausing pupae emerged as adults, whereas all non‐diapausing pupae died. Both egestion and assimilation were greater under long‐day conditions. The results revealed that pupae of this papilionid exhibit seasonal polyphenism in physiological and morphological traits. Energy from food appears to be expended on increasing cold hardiness in the overwintering generation and on reproduction in the non‐overwintering generation.     

Effects of transgenic Bt cotton on overwintering characteristics and survival of Helicoverpa armigera

The effects of transgenic Bt cotton on the overwintering generation of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), are unknown. We hypothesized that a Bt cotton diet may adversely affect fitness of this generation and examined fresh weight, lipids, glycogens, low-molecular-weight sugars and SCPs (supercooling points) of pupae, as well as survival of larvae, diapausing pupae and adult emergence in comparison with controls. Field and laboratory experiments showed that larvae fed on Bt cotton had a decreased pupation rate, and fewer entered diapause and emerged as adults compared with larvae fed non-Bt cotton. Furthermore, larvae fed Bt cotton had reduced pupal weight, glycogen content and trehalose levels both in diapausing and in non-diapausing pupae, and only diapausing pupae had an increased SCP compared to controls. The SCPs of diapausing pupae reared on Bt cotton were significantly higher than those reared on non-Bt cotton. The trehalose levels of diapausing pupae reared on Bt cotton were significantly lower than those of larvae reared on non-Bt cotton. Thus, these results suggest that a Bt cotton diet weakens the preparedness of cotton bollworm for overwintering and reduces survival of the overwintering generation, which will in turn reduce the density of the first generation in the following year. Effects of transgenic Bt cotton on the overwintering generation of cotton bollworm appear to have significantly contributed to the suppression of cotton bollworm observed throughout northern China in the past decade.     

Cold hardiness of diapausing and non-diapausing pupae of the European grapevine moth, Lobesia botrana

Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) is a key pest of grapes in Europe. It overwinters as a pupa in the bark crevices of the plant. Supercooling point (SCP) and low temperature survival was investigated in the laboratory and was determined using a cool bath and a 1 °C min^?1 cooling rate. Freezing was fatal both to diapausing and non‐diapausing pupae. SCP was significantly lower in diapausing male (?24.8 °C) and female (?24.5 °C) pupae than in non‐diapausing ones (?22.7 and ?22.5 °C, respectively). Sex had no influence on SCP both for diapausing and non‐diapausing pupae. Supercooling was also not affected by acclimation. However, acclimation did improve survival of diapausing pupae at temperatures above the SCP. Survival increased as acclimation period increased and the influence was more profound at the lower temperatures examined. Diapausing pupae could withstand lower temperatures than non‐diapausing ones and lethal temperature was significantly lower than for non‐diapausing pupae. Freezing injury above the SCP has been well documented for both physiological stages of L. botrana pupae. Our findings suggest a diapause‐related cold hardiness for L. botrana and given its cold hardiness ability, winter mortality due to low temperatures is not expected to occur, especially in southern Europe.     

X-ray investigation of gas bubble formation, and water loss in tsetse fly pupae

ABSTRACT. Using a microfocal X-ray apparatus, a gas bubble was detected within the puparium of Glossina morsitans. The bubble appeared between 6 and 15 h after pupariation and was associated with one of the longitudinal tracheal trunks of the third instar larva. The bubble grew and achieved maximum size approximately 96 h after pupariation. It then disappeared at the time of eversion of the pupal appendages. There was a close correlation between bubble size and the weight of water lost since the time of pupariation. At the time of eversion of the pupal appendages the gas bubble apparently passed out through the longitudinal tracheal trunk and posterior spiracle to occupy the space between larval (puparial) and pupal cuticle. It is suggested that the bubble plays a vital role in the separation of these cuticular layers and that to this end water loss from the puparium is essential.     

Suppression of net transpiration by multiple mechanisms conserves water resources during pupal diapause in the corn earworm Helicoverpa zea

One critical aspect of an insect's ability to overwinter successfully is the effective management of its water resources. Maintenance of adequate water levels during winter is challenging because of the prevailing low relative humidity at that time of year and the short supply of environmental water that is not in the form of ice. These issues are further exacerbated for insects overwintering as pupae, comprising an immobile stage that is unable to move to new microhabitats if conditions deteriorate. The present study compares the water balance attributes of diapausing and nondiapausing pupae of the corn earworm Helicoverpa zea Boddie, aiming to identify the mechanisms used by diapausing pupae to maintain water balance during winter. Diapausing pupae are 10% larger than nondiapausing individuals. Water loss rates for nondiapausing pupae are low (0.21 mg h^?1) and are suppressed (0.01 mg h^?1) in diapausing pupae. Cuticular lipids, which serve to waterproof the cuticle and thus suppress cuticular water loss, are more than two‐fold more abundant on the surface of diapausing pupae, and oxygen consumption rates during diapause drop to almost one‐third the rate observed in nondiapausing pupae. Water gain can be accomplished only when atmospheric water content is near saturation or during contact with free water. At moderate relative humidities (20–40%), water loss rates are very low for diapausing pupae, suggesting that these moth pupae have robust mechanisms for combating water loss. The exceptional ability of H. zea to suppress water loss during diapause is probably a result of the combined effects of increased size, more abundant cuticular lipids and decreased metabolic rates.     

Cold hardiness of Helicoverpa zea (Lepidoptera: Noctuidae) pupae

An insect's cold hardiness affects its potential to overwinter and outbreak in different geographic regions. In this study, we characterized the response of Helicoverpa zea (Boddie) pupae to low temperatures by using controlled laboratory measurements of supercooling point (SCP), lower lethal temperature (LT(50)), and lower lethal time (LLTime). The impact of diapause, acclimation, and sex on the cold hardiness of the pupae also were evaluated. Sex did not significantly affect the SCP, LT(50), or LLTime. However, the mean SCP of diapausing pupae (-19.3°C) was significantly lower than nondiapausing pupae (-16.4°C). Acclimation of nondiapausing pupae to constant temperatures from 10 to 20°C before supercooling also produced a significantly lower SCP than nondiapausing pupae held at 25°C. The LT(50)s of nondiapausing and diapausing were not significantly different, but confirmed that H. zea pupae are chill-intolerant because these lethal temperatures are warmer than the corresponding mean SCPs. Diapausing pupae survived longer than nondiapausing pupae at the same, constant, cold temperatures, a finding consistent with the SCP results. Both of these results suggest enhanced cold hardiness in diapausing pupae. When laboratory results were compared with field temperatures and observed distributions of H. zea in the contiguous United States, the laboratory results corroborated what is currently perceived to be the northern overwintering limit of H. zea; approximately the 40(th) parallel. Moreover, our research showed that areas north of this limit are lethal to overwintering pupae not because of low temperature extremes, but rather the length of time spent at near-zero temperatures.     

Blood protein synthesis in pupae of the silkmoth, Hyalophora cecropia

The blood proteins of pupae of Hyalophora cecropia were studied by acrylamide gel electrophoresis. Analyses of fractions separated on Sephadex G-75 columns revealed that a series of low molecular weight proteins previously reported to be absent in diapausing pupae are a normal component of diapausing pupal blood. Incorporation of isotopically labelled leucine into blood protein bands of injured pupae, perfused pupae, and perfused isolated pupal abdomens (lacking a midgut) revealed that each of these three preparations could synthesize all of the low molecular weight protein bands, with maximal incorporation in the perfused whole pupae.     

美国白蛾越冬蛹的过冷却能力、体内水分及脂肪含量

对美国白蛾(Hyphantrian cunea)越冬蛹在越冬过程中过冷却能力、体内水分及脂肪含量的变化进行了研究.结果表明：在越冬过程中,美国白蛾雌、雄蛹的抗寒能力呈现出相似的变化趋势, 即其抗寒能力随越冬期温度降低而逐渐增强, 并在冬季过后随温度升高而逐渐减弱.越冬期不同阶段越冬蛹体内水分、脂肪含量及过冷却点（SCP）和结冰点（FP）有所不同.其中,越冬前期和中期的SCP显著低于越冬后期,FP没有显著性差异;越冬中期蛹体内含水量最高,显著高于越冬前期和后期.越冬蛹的SCP和FP均显著低于非越冬蛹,体内水分和总脂肪含量均明显高于非越冬蛹.经回归分析,雌、雄蛹体内含水量与其SCP呈
较好的负相关关系（P<0.05）.     

寄主植物对棉铃虫越冬蛹抗寒能力的影响

通过对滞育蛹过冷却点的测定 ,初步明确寄主对棉铃虫Helicoverpaarmigera的越冬抗寒性有影响 ,幼虫取食棉花时产生的滞育蛹的过冷却点低于取食玉米的滞育蛹的过冷却点 ,即前者的抗寒能力高于后者 ;但用Bt棉喂养后的棉铃虫滞育蛹抗寒能力下降     

Debraining and diapause development in Manduca sexta pupae

Debraining experiments with wounded and normal controls were done at three different ages on diapausing Manduca sexta pupae of Kentucky and Illinois stocks. With early ages of both stocks debrained pupae escaped from diapause over an extended period of time, but wounded insects developed much earlier and at the same time as the normals. With later ages of Kentucky insects there was an immediate developmental response to wounding, and debrained insects showed initiation of pharate adult development over an extended period of time. With later ages of Illinois pupae both wounded and debrained animals showed an immediate developmental response. The responses of Illinois insects to debraining were shown to occur in insects overwintering under natural conditions. The results indicate that at least four endocrine states are possible for diapausing Lepidoptera pupae.     

Evaluation of the risk of overwintering Helicoverpa spp. pupae under irrigated summer crops in south-eastern Australia and the potential for area-wide management

Surveys were undertaken to determine the distribution of overwintering pupae of two species of Helicoverpa in south‐eastern Australia. The results indicate that significant populations of H. armigera have the potential to overwinter as pupae in the region under residues of their summer crop hosts. H. punctigera, conversely, was found not to overwinter in the region to any significant degree. The results also suggest that a high proportion of the overwintering H. armigera population are located in relatively few high risk fields. The overwintering population represents an ideal opportunity for control on an area‐wide basis using post harvest cultivation or “pupae busting”. The risk of overwintering H. armigera pupae occurring was largely associated with crop type, the mechanism being related to the date that the crop flowers, the level of pupal parasitism and the use of larval control measures. The results are discussed in terms of recommendations for farmers and it is suggested that a concerted effort to cultivate high risk fields has the potential to significantly reduce the population on an area‐wide basis.     

Water and carbohydrate levels at different developmental stages and dynamics in hibernating pupae of Pieris melete (Lepidoptera: Pieridae)

For insight into the physiological indicators of diapause in Pieris melete, water and carbohydrate (glycogen and trehalose) levels were measured under both natural and laboratory conditions. The highest water content (3.71–3.79 mg/mg dry weight) was found in larvae and developing pupae, which was substantially higher than in diapausing pupae (2.59 mg/mg dry weight). Water content was almost stable during diapause, except for individuals approaching diapause termination (3.43–3.58 mg/mg dry weight). The total carbohydrate level was significantly higher in pre‐pupae (47.41 μg/mg) compared to larvae (22.80 μg/mg) and developing pupae (21.48 μg/mg). The highest level of trehalose was detected in winter diapausing pupae, and no trehalose was found in larvae or developing pupae. Levels of glycogen were highest in pre‐pupae and lowest in diapausing pupae. Levels of total carbohydrate decreased as diapause proceeded, and no significant changes were found in trehalose levels for diapausing pupae under natural conditions or treated for 60–90 days at 5°C. Pupae treated at 20°C for 60–90 days had significantly lower levels of trehalose than those treated for 30 days. Glycogen content was relatively stable at 5°C, but increased after treatment under natural conditions and 20°C for more than 60 days. These results suggest that the dynamics of water and carbohydrate levels are potential physiological diapause indicators, which show metabolic differences between trehalose and glycogen during diapause development.     

Effect of soil moisture on overwintering pupae in Spodoptera exigua (Lepidoptera: Noctuidae)

Spodoptera exigua Hübner (Lepidoptera: Noctuidae), can overwinter as pupae at depths of 0- to 5-cm beneath the ground. In order to understand the effect of soil moisture on the overwintering success of this species, we tested the supercooling point and survival of pupae, and the growth rate of prepupae that were exposed to different temperature and soil moisture in the laboratory. Results showed that supercooling points, body water contents, and survivals after the different pre-treatments were not significantly affected by the soil moisture. The developmental progress of prepupae, survival of prepupae and pupae were negatively correlated with soil moisture as well as the delay of exposure time, which supports the hypothesis that soil moisture acts as a developmental modulator. We presumed that the delay of pupation and lower prepupae survival under higher soil moisture was due to lack of a complete pupal chamber for protection at low temperatures. Low pupal survival was likely attributed to lack of oxygen in the soil, especially under the condition of higher soil moisture. We suggest that using strategies of irrigation and soil tillage during winter may decrease the overwintering population of S. exigua from the perspective of integrated pest management.     

高温条件下棉铃虫化蛹率、夏滞育率和蛹重的变化

在预蛹期,高温处理能诱导棉铃虫蛹进入夏滞育。本实验着重就33～39℃的变温下滞育蛹和未滞育蛹的失重动态进行了对比研究,同时以常温（27℃）下蛹作为参照。研究发现： 在33～39℃的变温条件下,棉铃虫化蛹率显著低于其在常温下的化蛹率,且所化蛹中有63.2%的雄性和10.9%的雌性进入高温夏滞育,其中高温滞育蛹和未滞育蛹分别都轻于正常发育蛹。化蛹后第2日至第5日期间,高温滞育蛹失重量显著低于高温未滞育蛹和正常发育蛹的失重量,分别为3.62、13.30和5.49 mg;蛹期总失重量结果与化蛹后第2～5日间蛹失重量趋势一致,高温滞育蛹、未滞育蛹和正常发育蛹失重量分别为15.60、49.35和26.30 mg。蛹失重动态研究发现高温滞育蛹在夏滞育期间其失重曲线平缓,显著低于高温未滞育蛹和正常发育蛹;高温滞育蛹滞育解除后,其失重曲线与正常发育蛹的失重趋势基本一致。结果表明,棉铃虫夏滞育蛹能通过维持低的代谢水平来度过不利环境,具有一定的生态适应意义。     

Effects of thermophotoperiod on growth parameters of Helicoverpa armigera

The effects of photoperiod and temperature on growth parameters of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) were investigated under laboratory conditions by exposing its larvae to fluctuating and alternating temperature regimes. Our data made evident that the interplay between photoperiod and temperature has a direct effect on growth parameter responses of H. armigera. However, the type of temperature regime (fluctuating or alternating) may enhance or diminish the effects of photoperiod. With fluctuating temperature, larval developmental time was significantly reduced with increasing photophase, irrespective of the diapause status later in the pupal stage; the lowest value was observed under continuous light conditions. With alternating temperature, larval developmental time was significantly decreased with the reduction in temperature amplitude, and with the coincidence of the thermophase with the scotophase. At both temperature regimes, no significant differences in pupal weight were observed between diapausing and non‐diapausing individuals, although, in most treatments, the diapausing pupae tended to be heavier than the non‐diapausing ones. The increased pupal weight of individuals destined for diapause is probably related to their longer larval developmental time. Knowing the effects of these factors on the variation of H. armigera growth is necessary in explaining phenomena associated with immature stages, and can lead to a more profound understanding of the potential for this insect to evolve in response to environmental changes.     

Variations of biogenic amine levels in the brain of Pieris brassicae pupae during nondiapausing and diapausing development

The post-embryonic development of Pieris brassicae can either be continuous (under a long photoperiod) or interrupted at the pupal stage (induced by a short photoperiod); this phenomenon is termed facultative diapause. Several studies have indicated that certain brain mechanisms could be directly involved in the perception of variations in the photoperiod and could mediate some physiological effects particular to dormancy. Biogenic amines have been particularly implicated in the response to photoperiod variations and also in the regulation of development, especially in diapause induction and termination. High performance liquid chromatography with dual electrochemical detection has therefore been used to measure several biogenic amines in pupal nervous tissues at various stages of nondiapausing and diapausing development. During direct development, the levels of dopamine (DA) and N-acetyldopamine (NADA: a DA metabolite) in brain were relatively high in 3-day-old pupae and at the end of pupal life (on the 8th day). Dihydroxyphenylacetic acid (another metabolite of DA) showed no variation. Serotonin was mainly observed in 2–3-day-old pupae but 5-hydroxyindoleacetic acid was never detected. In young diapausing insects, similar variations of DA levels were observed even though a slight decrease of DA metabolites was noted. Serotonin appeared somewhat later (4–5 days) and attained higher levels. In late diapausing pupae, a marked increase in DA levels was observed, especially when pupae were kept at low temperature (4°C). During diapause, serotonin levels were reduced or even absent.     

酪蝇蛹对其成虫的引诱效果

室内采用Y型嗅觉仪测定酪蝇蛹、蛹壳及蛹的正己烷提取液对酪蝇成虫的引诱效果.结果表明:酪蝇的蛹、蛹的正己烷提取液对雌、雄成虫有明显的引诱,随着蛹量的增加其对雄虫的引诱效果增加,对雌虫的引诱效果下降;提取液浓度为5～12.5头当量/mL时,对雌、雄成虫有明显的引诱效果,但在浓度为2.5头当量/mL时对雄虫有明显的驱避效果,雌性蛹壳对两性成虫有明显的引诱效果,而雄性蛹壳只对雄虫有明显的引诱效果,对雌虫有明显的驱避效果.     

土壤含水量及蛹室对甜菜夜蛾蛹越冬的影响

研究了自然条件下土壤含水量和蛹室对甜菜夜蛾Spodoptera exigua Hübner蛹越冬的影响,发现蛹在自然蛹室中能存活30d以上(不超过60d)。处理15d,随着土壤含水量的变化,蛹的存活率分别降至80%、20%和43%。但处理30、60、90和120d时死亡率均达到100%。调查发现,随着处理时间的延长,各土壤含水量中所埋的蛹死亡特征均有一个相同趋势,即发黑、发霉——肿胀——腐烂——残留部分蛹体。不同土壤含水量条件下,蛹的过冷却点、结冰点和蛹体含水量间均存在显著性差异(P≤0.05),尤以在最低的土壤含水量条件下蛹的过冷却点、结冰点和蛹体含水量最低,分别为(-20.2±1.1)℃、(-11.95±2.5)℃和(57.6±7.7)%。在室外变温条件下,结果初步表明蛹室对蛹有一定的保护作用。     

Comparison of cold hardiness and sugar content between diapausing and nondiapausing pupae of the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract. To understand overwintering of the cotton boll worm Helicoverpa armigera, cold hardiness and sugar content are compared between diapausing and nondiapausing pupae. Diapausing and nondiapausing pupae reared at 20 °C under short and long photoperiods are acclimatized with a reduction of 5 °C per 5 days to 0 °C. When the acclimation temperature reaches 0 °C, the survival of diapausing pupae is assessed. The survival gradually decreases as the period of treatment progresses and approximately half survive for 112 days. However, nondiapausing pupae survive only 14 days after exposure to 0 °C. The surpercooling points of nondiapausing, diapausing and acclimatized pupae are approximately −17 °C. The major sugars contained in pupae are trehalose and glucose. Even though trehalose contents in diapausing pupae (initial level: 0.6 mg 100 mg⁻¹ fresh weight) increase significantly during cold acclimation and continue increasing until 58 days after exposure to 0 °C (maximum level: 1.8 mg 100 mg⁻¹), glucose is maintained at low levels (0.02 mg 100 mg⁻¹) for 56 days at 0 °C. However, glucose contents increase (maximum level: 0.8 mg 100 mg⁻¹) with decreasing contents of trehalose 84 days after exposure to 0 °C. Glycogen content gradually decreases during cold acclimation. When nondiapausing pupae are acclimatized with a reduction of 5 °C per 5 days to 5 °C from the beginning of pupation until the eyespots move, trehalose content increases (maximum level: 1.0 mg 100 mg⁻¹). Glucose contents in nondiapausing pupae increase before eclosion (0.09 mg 100 mg⁻¹). From these results, diapausing pupae of H. armigera can overwinter in regions where average winter temperatures are higher than 0 °C, but nondiapausing pupae cannot.     

Water loss and respiration of Lucilia cuprina during development within the puparium

The rate of loss of water and the rate of uptake of oxygen were measured continuously throughout the development of Lucilia cuprina within the puparium. Changes in these parameters were correlated with changes observed in morphology of cuticles and respiratory structures during development.In development at 26°C, there is, at 20–22 hr after puparium formation a major loss of water by mechanical expulsion of moulting fluid chiefly through the posterior larval spiracles after the severing of the posterior larval tracheae. This loss of water is essential to survival and is followed by an extremely low rate of water loss attributed to slow diffusion of water through the resulting air gap between the pupal cuticle and the puparium. There is an increase in oxygen consumption during the pupal movements associated with the casting of the larval tracheae followed by a sharp reduction in oxygen consumption until the pupal horns are everted a short time later. This combination of physiological events enables development to proceed over a wide range of conditions in the puparial environment.