大斑芫菁滞育幼虫在滞育不同阶段体内糖类和醇类含量的变化

在以卵滞育的昆虫中昆虫滞育时的生理代谢特点已经得到了大量研究。本文对以末龄幼虫（5龄）滞育的大斑芫菁Mylabris phalerate（Pallas）在不同滞育阶段体内糖类和醇类代谢的特征进行了研究。结果表明： 滞育个体血淋巴中的海藻糖含量高于非滞育个体,且随滞育时间的加大逐渐升高,滞育5个月时达到最大值,为5.61 μmol/mL。糖原的含量随滞育的进程逐渐减少,滞育初期（0.5个月）为0.72 mg/mL,到滞育末期（5个月）时仅为0.1 mg/mL。滞育个体脂肪体中的海藻糖含量都高于非滞育个体,滞育1个月时为非滞育个体的3倍,至滞育末期时达非滞育个体的5倍,为2.5 μmol/g脂肪体。糖原含量总体变化趋势是随滞育时间的加大逐渐减少,滞育早期和中期都高于非滞育个体。在滞育过程中血淋巴积累的小分子多元醇主要为甘油,其次是山梨醇;而在脂肪体中主要为甘油,其次是甘露醇,少量积累山梨醇：表明大斑芫菁滞育幼虫主要积累的是海藻糖和一些小分子多元醇。滞育幼虫在准备滞育时储备了大量糖原,这些糖原可能为滞育期间海藻糖、山梨醇和甘油的代谢提供了原料。     

Cold hardiness and sugar content in photo‐insensitive individuals of the cotton bollworm Helicoverpa armigera

Abstract A proportion of Helicoverpa armigera collected from fields in Okayama Prefecture (Western Japan; 34.6°N, 134.1°E) does not enter diapause when reared under a short days at 20 °C during the larval stages. However, diapause in such photo‐insensitive individuals can be induced when they are reared at moderately low temperatures, such as 15 °C, regardless of photoperiod. To determine whether such photo‐insensitive individuals can survive overwintering in fields, the present study compares the cold hardiness and sugar content between nondiapausing and diapausing pupae of photo‐insensitive individuals selected over several generations at 20 °C under a short day photoperiod (LD 10 : 14 h). Diapausing and nondiapausing pupae are obtained under the short days by rearing at 15 and 20 °C, respectively, during larval and pupal stages. These pupae are stepwise acclimated at a reduction of 5 °C every 5 days to 0 °C. Maximum survival periods of nondiapausing and diapausing pupae at 0 °C are approximately 30 and 90 days, respectively. Trehalose content in diapausing pupae increases, reaches a maximum level (1.95 mg 100 mg^?1 in males and 2.1 mg 100 mg^?1 in females) 28 days after exposure to 0 °C and then decreases. On the other hand, glucose content in diapausing pupae increases (maximum level: 0.32 mg 100 mg^?1 in males and 0.21 mg 100 mg^?1 in females) with decreasing trehalose content 42 days after exposure to 0°C. The decrease in trehalose content and the increase in glucose content may be linked to termination of diapause in H. armigera. These results suggest that, in Japan, the photo‐insensitive individuals can only survive in the mild winters of southern regions, and not in the severe winters of northern regions.     

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.     

Metabolic dynamics across prolonged diapause development in larvae of the sawfly,Cephalcia chuxiongica (Hymenoptera: Pamphiliidae)

Nutrient metabolism is crucial for the survival of insects through the diapause. However, little is known about the metabolic mechanism of prolonged diapause. The sawfly, Cephalcia chuxiongica (Hymenoptera: Pamphiliidae), is a notorious defoliator of pine trees in southwest China. One of the distinguishing biological characteristics of this pest is the prolonged diapause of about 1.5 years. In this study, the body lipid, carbohydrate (total body sugar, glycogen, trehalose, and glucose), protein, and glycerol contents were measured in diapausing larvae of C. chuxiongica. The results showed that the changes of biochemical composition in C. chuxiongica are associated with the diapause initiation, maintenance, and termination phases. During the initiation phase, trehalose, glucose, and glycerol increased significantly, but glycogen decreased sharply. In general, the lipid, carbohydrate, and glycerol levels decreased gradually across the maintenance phase. At termination phase, the contents of glycogen and lipid persistently decreased, while an increase of trehalose, glucose, and glycerol contents were detected. The protein level was significantly higher at maintenance phase than at initiation and termination phases. It was also found that elevation of trehalose, glucose, and glycerol contents occurred in winter. These implies that the metabolites with altered levels in diapausing larvae of C. chuxiongica are responsible for maintaining a prolonged development and overwintering.     

麦红吸浆虫幼虫滞育期间糖类物质变化

分析研究了麦红吸浆虫Sitodiplosis mosellana (Gehin) 幼虫滞育期间总糖、海藻糖和糖原含量的变化。结果表明： 不同滞育年限幼虫的总糖含量无显著差异。在滞育年周期中,不同时期的滞育幼虫总糖含量明显不同。幼虫老熟入土滞育以前的总糖含量明显高于入土滞育期间。入土滞育过程中,越冬期和春季的总糖含量明显高于夏季和秋季。同期的裸露幼虫与结茧幼虫的总糖含量仅在秋季有一定的差异,其他时间基本相似。结茧幼虫滞育期间的海藻糖含量一直维持较高的水平,说明其滞育期间的糖醇积累型属于海藻糖积累型;秋季与春季糖原含量的增加可能与麦红吸浆虫的滞育解除或滞育强度的变化有一定的关系。     

Effects of photoperiod and temperature on diapause induction and termination in the swallowtail,Sericinus montelus

Abstract Sericinus montelus overwinters as diapausing pupae. In the present study, the effects of photoperiod and temperature on diapause induction and termination of diapause are investigated. The results obtained demonstrate that high temperature can reverse the effect of short day‐lengths on diapause induction. Under an LD 12 : 12 h photoperiod, all pupae enter diapause at 15, 20 and 25 °C, whereas all pupae develop without diapause at 35 °C. No pupae enter diapause under an LD 14 : 10 h photoperiod when the temperature is above 20 °C. Photoperiodic response curves obtained at 25 and 30 °C indicate that S. montelus is a long‐day species and the critical day‐length is approximately 13 h at 25 °C. At 25 °C, the duration of diapause is shortest when the diapausing pupae are maintained under an LD 16 : 8 h photoperiod and increases under LD 14 : 10 h and LD 12 : 12 h photoperiods. Under an LD 16 : 8 h photoperiod, the duration of diapause is shortest when the diapausing pupae are maintained at 25 °C, followed by 20 and 30 °C, and then at 15 °C. These results suggest that a moderate temperature favours diapause development under a diapause‐averting photoperiod in this species. The duration of diapause induced by an LD 12 : 12 h photoperiod is significantly longer at 25 °C than those at 15, 20 and 30 °C, and is shortest at 15 °C. At 25 °C, the duration of diapause induced by LD 6 : 18, LD 12 : 12 and LD 13 : 11 h photoperiods is similar and longer than 90 days. Thus, the diapause‐inducing conditions may affect diapause intensity and a photoperiod close to the critical day‐length has significant influence on diapause intensity in S. montelus.     

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.     

Physiology of diapause and cold hardiness in overwintering pupae of the apple leaf miner Phyllonorycter ringoniella in Japan

Abstract The apple leaf miner Phyllonorycter ringoniella (Matsumura) (Lepidoptera: Gracillariidae) overwinters as a diapausing pupa. The diapause rate reaches 100% in early October. Diapause intensity decreases gradually from early October and diapause terminates in early February. The fresh body weight of diapausing pupae is 1.6 times that of non-diapausing pupae. The main cryoprotectant in P. ringoniella pupae is trehalose. Three stages are distinguishable as indicated by the correlations between diapause intensity, levels of cold hardiness and the trehalose content: diapause induction occurred in October, diapause development from November to December, and post-diapause quiescence from January to April. During diapause induction, the pupae accumulate low levels of trehalose and do not survive exposure to −15 °C. During diapause development, the pupae gradually accumulate more trehalose and show some ability to survive exposure to −15 °C, but not to −20 °C. During post-diapause quiescence, the pupae accumulate relatively more trehalose and cold hardiness fully develops, but decreases quickly in April. The trehalose content in pupae sampled in December is unaffected by acclimation temperatures in the range 0–30 °C, but decreases in pupae sampled in March after acclimation at temperatures from 5 to 15 °C. These results suggest that overwintering pupae of P. ringoniella have the ability to accumulate trehalose and develop a high level of cold hardiness during diapause development.     

取食Bt棉与玉米的越冬代棉铃虫抗寒性特征比较

【目的】针对由Bt棉花和玉米构成的华北农田景观, 探讨不同寄主作物对棉铃虫 Helicoverpa armigera 越冬抗寒的影响。【方法】2013年在河北廊坊科研中试基地的作物田中将棉铃虫幼虫接到Bt棉和玉米上, 比较取食不同作物后棉铃虫的化蛹率、存活率和越冬蛹羽化率;在室内控制条件下分别用棉蕾和鲜玉米粒饲喂棉铃虫幼虫。 测定滞育蛹和非滞育蛹的鲜重、干重、以及脂肪、糖原和低分子物质含量等指标, 比较取食不同作物后棉铃虫的抗寒能力。【结果】取食玉米的棉铃虫滞育蛹干重（117.5 mg）、脂肪含量（457.2 μg/mg DW）以及海藻糖浓度（86.45 μg/g）均显著高于取食Bt棉的棉铃虫滞育蛹干重（56.6 mg）、脂肪含量（239.6 μg/mg DW）以及海藻糖浓度（13.87 μg/g）;取食玉米的棉铃虫冰点(-10.2℃)显著低于取食Bt棉的棉铃虫冰点(-6.5℃)。【结论】结果表明取食玉米更加有利于棉铃虫越冬。 据历史数据, 近年来玉米种植面积不断增加, 这将提高棉铃虫成功越冬比率, 对棉铃虫种群扩张起到促进作用, 因此注重玉米上棉铃虫的防治尤为重要。     

Effects of acclimation and diapause on the cold tolerance of Trogoderma granarium

Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a pest of stored grain in Africa, Asia, and Europe. It is a quarantine insect for much of the rest of the world. Control of T. granarium can be achieved with methyl bromide, but this fumigant is an ozone‐depleting substance and is being phased out worldwide. Thus, there is an urgent need to find new methods of control, including the use of low temperatures. Here, we assess the effects of diapause and cold acclimation on the cold tolerance of T. granarium. The percentage of larvae in diapause increased with larval density, reaching 57.3% when reared at a density of 73 larvae g^?1 diet. The cold tolerance of T. granarium was assessed by the supercooling points (SCPs) of various life stages. The SCP of non‐acclimated insects ranged from ?26.2 ± 0.2 °C (mean ± SEM) for eggs to ?14.4 ± 0.4 °C for larvae. The lowest SCP for larvae, ?24.3 ± 0.3 °C, was obtained for diapausing‐acclimated larvae. Based on mean LT₅₀ values, the most cold‐tolerant stage at ?10 °C was the diapausing‐acclimated larvae (87 days) followed by non‐diapausing‐acclimated larvae (51 days), diapausing non‐acclimated larvae (19 days), adults (4 days), non‐diapausing non‐acclimated larvae (2 days), pupae (0.4 days), and eggs (0.2 days). The estimated times to obtain 99.9968% mortality (Probit 9) for diapausing‐acclimated larvae are 999, 442, 347, 84, and 15 days at 0, ?5, ?10, ?15, and ?20 °C, respectively. Probit 9 is an estimated value used by quarantine experts to estimate conditions that are required to kill all insects. In light of the long exposure time needed to control T. granarium even at ?20 °C, cooling to below ?27 °C (i.e., below the SCP of eggs) will quickly kill all life stages and may be the best way to control this insect with low temperatures.     

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.     

Regulation of heat shock proteins in the apple maggot Rhagoletis pomonella during hot summer days and overwintering diapause

Abstract Developing larvae of the apple maggot Rhagoletis pomonella are frequently exposed to summertime apple temperatures that exceed 40 °C and, during their overwintering diapause, pupae are exposed to sub‐zero soil temperatures for prolonged periods. To investigate the potential involvement of heat shock proteins (Hsps) in response to these environmental extremes, the genes encoding Hsp70 and Hsp90 in R. pomonella are cloned and expression monitored during larval feeding within the apple and during overwintering pupal diapause. Larvae reared in the laboratory at constant temperatures of 25, 28 or 35 °C express Hsp90 but very little Hsp70. Larvae do not survive rearing at 40 °C. The temperature cycles to which larvae were exposed inside apples in the field, ranging 16–46.9 °C over a 24‐h period, elicit strong Hsp70 and Hsp90 expression, which begins at mid‐day and reaches a peak in late afternoon, coinciding with peak air and apple temperatures. Heat shock proteins are also expressed strongly by pupae during their overwintering diapause. Hsp70 is not expressed in nondiapausing pupae but is highly expressed throughout diapause. Hsp90 is constitutively expressed in both diapausing and nondiapausing pupae. Rhagoletis pomonella thus strongly expresses its Hsps during pupal diapause, presumably as a protection against low temperature injury, and during larval development to cope with natural temperature cycles prevailing in late summer.     

Effect of photoperiod and temperature on diapause in a Florida strain of the tropical warehouse moth Ephestia cautella

A photoperiodically-controlled diapause of the long-day, short-day type was identified in a brown-winged, yellow-eyed strain of Ephestia cautella (Walker). The proportion of larvae diapausing in very long photoperiods was less than in short photoperiods. The mean critical photoperiod, here defined as that photoperiod giving half the maximum percentage of insects that diapause in response to photoperiod at a given temperature, was between 12 and 13 hr for the long-day reaction at both 20 and 25°C. The principal sensitive phase occurred near the time of the last larval moult. The mean duration of diapause was 2–3 months at 20°C and slightly longer at 25°C. The optimum temperature for diapause development was near 15°C, all larvae pupating within 24 days after a 45-day exposure at this temperature. Diapause could be terminated whenever larvae diapausing at 20°C were exposed to as few as five long (15 hr) photoperiods at 25°C. Long photoperiods at 20°C, or short photoperiods (9 hr) at 25°C were less effective in terminating diapause.     

Developmental and metabolic changes induced by anoxia in diapausing and non-diapausing flesh fly pupae

Summary Anaerobic metabolism was compared in nondiapausing (ND) and diapausing (D) pupae of the flesh fly,Sarcophage crassipalpis using in vivo¹³C NMR spectroscopy. Anoxia-induced changes in the development of ND and D pupae were correlated with oxidative metabolism and mitochondrial integrity. ND pupae tolerated 1 day of anoxia without any obvious developmental effect, while D pupae tolerated up to 6 days of anoxia. Longer exposure to anoxia (3 days in ND pupae and up to 14 days in D pupae) allowed development to the pharate adult stage but precluded eclosion. Four-day anoxia applied to ND pupae during 4–6 days post-pupariation arrested development in a stage indistinguishable from diapause. This morphological stasis was accompanied by 80% suppression of oxidative metabolism and a 100% increase in glycerol concentration. However, unlike a true diapause, this arrest could not be terminated with 20-hydroxyecdysone or hexane. Four-day anoxia treatment applied to D pupae stimulated development and raised their oxygen consumption. The anoxia-induced changes in oxidative metabolism were not accompanied by mitochondrial changes. Exposure to 95%PO₂ atmosphere had no apparent developmental or metabolic effects on ND or D pupae. Major metabolites (lipids, trehalose, glycogen, glycerol, glutamine, and alanine) were detected in the ND and D pupae but their rates of turnover differed. Anoxia induced synthesis of glycerol and alanine in both D and ND pupae. Injected labeled glucose was incorporated primarily into trehalose and glycogen by both D and ND pupae. The rate of incorporation in ND pupae was approximately twice that observed in D pupae. Anoxia resulted in glycerol and alanine synthesis in both groups of pupae, but more glycerol was labeled in ND pupae and more alanine in D pupae. Glycogen and trehalose were depleted in the D pupae under anoxia. Cold acclimation had no effect on the steady-state or rate of synthesis of metabolites.     

Metabolic reserves associated with pupal diapause in the flesh fly, Sarcophaga crassipalpis

Larvae of Sarcophaga crassipalpis destined for pupal diapause (light:dark 12:12, 20°C) contain nearly twice as much lipid and twice the haemolymph protein concentration as larvae that will not enter diapause (light:dark 15:9, 20°C). This conspicuous difference in metabolic reserves provides the earliest indication of the developmental fate of the larva. Lipid reserves are utilized rapidly during the first half of diapause and then remain stable until adult eclosion. In contrast, residual dry weight changes very little early in diapause but drops sharply late in diapause, thus implying a transition from lipid utilization to protein or carbohydrate utilization in mid-diapause. We suggest that this metabolic transition marks the end of the “fixed latency period”: pupae readily respond to environmental or hormonal stimulation after this point. Diapause-destined larvae did not accumulate more glycogen than nondiapause-destined larvae, but an 80% decrease in glycogen at the onset of diapause and its elevation at the end of diapause suggests the utilization of glycerol or related compounds as cryoprotectants during diapause. Profiles of water content are very similar in short-day and long-day flies, thus suggesting that dehydration is not a mechanism exploited by the flesh fly to achieve cold hardiness. Adult flies that have experienced pupal diapause emerge from the puparium with lipid, glycogen, and water content nearly identical to flies that have not experienced diapause, but the residual dry weight is much lower. The severe depletion of protein may account for the reduced fecundity of flies that have experienced diapause.     

CARBOHYDRATE METABOLISM IN THE EGGS OF THE SILKWORM, BOMBYX MORI. I. ABSENCE OF PHOSPHOFRUCTOKINASE IN THE DIAPAUSING EGG

In the diapausing eggs of the silkworm, Bombyx mori , glycogen is rapidly converted to sorbitol and glycerol, and this conversion is reversed at termination of the diapause (C hino , 1958). To elucidate the pathway leading to this polyol formation and its regulatory mechanisms, enzymes concerning carbohydrate metabolism were surveyed in diapausing as well as in developing eggs of the silkworm.
Most of the enzyme activities concerning citric acid cycle are low at the beginning of the embryogenesis and during diapause, but increase at the later stages of the development. Making an exception, reduction rate of malate and fumarate was rather high from the onset of the embryonic development. Several glycolytic enzymes were also studied. Most remarkable fact is that phosphofructokinase activity could not be demonstrated in the diapausing and also in the early stages of the developing eggs. Other enzymes, viz. α-glycerophosphate dehydrogenase, aldolase, glyceraldehyde-3-phosphate dehydrogenase were detected from the beginning of the embryogenesis.
Absence of phosphofructokinase, together with the high activity in glucose-6-phosphate dehydrogenase, suggests that predominant pathway in carbohydrate metabolism in the early stages of embryogenesis and in the diapause period is by way of pentose phosphate pathway. This supposition is confirmed by the experiments using labeled glucose. Incorporation of the label into glycerol of the diapausing eggs was three to four fold when G-6-¹⁴C was injected into pupae as compared with the case of G-1-¹⁴C injection. The above experiments provide evidence supporting the theory that glycogen is converted into sorbitol and glycerol mostly by way of the pentose phosphate pathway in the diapausing eggs.     

Ecdysteroids and diapause in pupae of Heliothis punctiger

Most pupae of H. punctiger enter diapause when reared at 19°C, 12L:12D. When pharate pupae were treated for only 12 hr at 28°C about 50% developed at 19°C. The proportion of non-diapausing pupae increased as the temperature at which the pharate pupal stage was spent increased.The quantity of injected 20-hydroxyecdysone necessary to promote development in diapausing pupae varied from about 1 μg g^?1 soon after pupation to about 4 μg g^?1 after 50 days. It fell somewhat after 150 days.Removing brains from non-diapausing pupae showed that the brain secreted its hormone at the time of pupation (or just before). However, if the pupae were kept at 19°C development did not occur unless the brain remained in situ for at least 20 hr at 28°C. Implanting brains from non-diapausing pupae into diapausing ones had no measurable effect.These results may be explained by postulating that the prothoracic gland is ‘activated’ by exposure to high temperature, but that it reverts to inactivity over a period at 19°C. The ‘active’ gland must then be stimulated by brain hormone for a long period to trigger secretion of its hormone, which results in development. Diapause is thus the result of the failure of the prothoracic gland to secrete.     

Thermal responses in the citrus fruit fly,Dacus tsuneonis: evidence for a pupal diapause

Thermal responses controlling pupariation and adult eclosion in a citrus fruit fly,Dacus tsuneonis (Miyake), were studied to understand the winter biology of this species. When mature larvae were exposed to various temperature conditions, the highest percentage of pupariation was obtained at 15 °C, although the variance at this temperature was greater than at 20 °C or 25 °C. Pupariation occurred most rapidly at 20 °C and an alternating temperature with a mean of 15 °C. At constant 15 °C, pupae failed to emerge as adults. Pupae were characterized by a reduced respiration rate, which is typical of a diapausing pupa. When insects were stored at different temperatures for 45 days after pupariation, and then transferred to 25 °C, adult eclosion occurred earlier when the initial temperature was 10 °C than when it was 5 °C or 15 °C. Adult eclosion occurred most synchronously and pupal mortality was lowest when insects were stored at 15 °C for 90 days before incubation at 25 °C. These results strongly suggest thatD. tsuneonis enters a pupal diapause.     

Glycerol accumulation in developmentally arrested pupae of Papilio machaon obtained by brain removal

Brains were removed from non-diapausing pupae of Papilio machaon within 24 hr after pupation. The developmentally arrested pupae were examined for glycerol metabolism by comparison with naturally diapausing pupae. The decerebrate non-diapausing pupae accumulated appreciable amounts of glycerol (13.0 mg/ml haemolymph) during exposure to 5°C for 2 months. However, this amount was considerably lower than that accumulated in the naturally diapausing pupae (24.5 mg/ml) under the same conditions. A difference was also observed in the initial level of the glycogen in the fat body. The naturally diapausing pupae contained about 105 mg/g glycogen, while the decerebrate non-diapausing pupae contained only about 70 mg/g, one day after pupation.     

Induction of larval diapause in the blowfly, Calliphora vicina R.-D. (Diptera, Calliphoridae) under field and laboratory conditions

Field experiments conducted in the environs of St. Petersburg (Russia) with a local population of Calliphora vicina showed that induction of larval diapause under natural conditions was significantly dependent on day lengths and temperature. The maternal photoperiodic response had a distinct threshold: the first diapausing larvae hatched from the eggs laid in the middle of August when the day length was 16 h; at shorter photoperiods, the fraction of diapausing larvae depended only on temperature. At the mean temperature of 16°C, larval diapause was rarely recorded; at 12–13°C, about 50% of the larvae entered diapause; at 7–9°C, nearly all the larvae entered diapause. These results of the field experiments agree well with the parameters of photoperiodic and thermal responses studied in the laboratory at constant temperatures and photoperiods.