Impact of short‐term exposure to low subzero temperatures on egg hatch in the hemlock looper,Lambdina fiscellaria

The frequency of extreme events, such as cold spells, is expected to increase under global warming. Therefore, the ability of insects to survive rapid changes in temperature is an important aspect to investigate in current population ecology. The hemlock looper (HL), Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), a defoliator of boreal balsam fir forests in eastern Canada, overwinters at the egg stage on tree trunks and branches where eggs can be exposed to very low subzero air temperatures. Using eggs from the island of Newfoundland (NL) and Quebec mainland (QC), we undertook field and laboratory experiments to determine: (1) their supercooling point (SCP) in mid‐January and mid‐February; (2) overwintering mortality; (3) cold tolerance to various combinations of subzero temperatures (?25, ?30, ?33, ?35, or ?37 °C) and exposure durations (2, 4, 8, 12, or 16 h); and (4) potential causes of death at subzero temperatures above the SCP. Regardless of population or sampling date, eggs supercooled on average at ?40.1 °C. In the field, 59% of eggs from either population that overwintered in Sainte‐Foy (QC) and Corner Brook (NL) hatched successfully, whereas none did in Armagh (QC) or Epaule (QC). In the laboratory, 50% of eggs survived after 4 h at ?34.4 °C or after 14 h at ?32.9 °C. In contrast, regardless of exposure duration, >50% of eggs hatched at temperatures ≥?33 °C, but <50% did so at ≤?35 °C, suggesting high pre‐freeze mortality. However, when eggs were attached to thermocouples and exposed to temperatures ranging from ?25 to ?37 °C for 16 h, 69% froze at temperatures of ?35 to ?37 °C, but only 2% did at ?25 or ?30 °C. Time to freeze decreased as subzero temperatures declined, and this was more evident in island eggs than in mainland eggs. Overall, eggs can freeze after a brief exposure to subzero temperatures higher than the standard SCP, and are thus highly vulnerable to cold spells.     

Influence of balsam fir (Abies balsamea) budburst phenology on hemlock looper (Lambdina fiscellaria)

Many herbivorous insects emerge synchronously with budburst of their host plant, as the nutritional quality of foliage often decreases rapidly following budburst. We carried out manipulative field experiments to evaluate the influence of bud and shoot phenology on performance of the hemlock looper, Lambdina fiscellaria Guenée (Lepidoptera: Geometridae: Ourapterygini), on balsam fir, Abies balsamea (L.) Mill. (Pinaceae), in NF, Canada. Hemlock looper survival, pupal weight, and realized fecundity, which were then combined to estimate fitness, were all highest when newly emerged first instars were placed on foliage of current‐year shoots that had completed approximately 25–35% of their elongation, and lower when placed on younger or older foliage. Survival of a small portion of larvae placed on buds a week before budburst suggests that newly emerged first instars either entered unburst buds or survived for a week without food. In laboratory experiments, approximately half of larvae survived for 4 days without food or water at 10 °C and 65% r.h. The timing of egg hatch in the field appeared to be adaptive, but the short duration of egg hatch suggests that another factor in addition to host plant phenology exerts stabilizing selection pressure on the timing of egg hatch.     

Reproductive performance of the hemlock looper,Lambdina fiscellaria,as a function of temperature and population origin

In a recent study of the hemlock looper (HL), Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), long exposure of early‐diapausing eggs to high temperatures considerably reduced their ability to hatch. This finding raised the possibility that adults could also be negatively affected by increasing temperatures if they reproduced too early in the season in response to global warming. To investigate this hypothesis, newly formed HL pupae from three populations of eastern Canada ‐ Quebec (QC), Newfoundland (NL), and Labrador (LB) ‐ were submitted to four constant temperatures (10, 15, 20, or 25 °C) during pupal and adult development. The effect of population origin on HL reproduction was generally negligible. Mating probability was high at 15 and 20 °C (0.86 and 0.83, respectively), quite low at 10 °C (0.53), and even lower at 25 °C (0.38). Mating started earlier in the night and lasted longer as temperature decreased. Both productivity and absolute fecundity increased when temperature increased from 10 to 15 °C and then decreased slowly as temperature increased further. Over populations and temperatures, relative fecundity averaged 0.95, indicating that females had enough time to lay most of their eggs before they died. High temperatures had a deleterious effect on egg fertility: between 10 and 20 °C, relative fertility was about 0.90, but it dropped to 0.51 at 25 °C. The average proportion of fertile eggs declined from 0.88 in the first quarter of the egg‐laying period to 0.57 in the last quarter, suggesting lower sperm count or viability, or deterioration of the oocytes as the egg‐laying period progresses. Based on these findings, we argue that the production of an additional fifth instar among HL populations of southern origin can be viewed as an adaptive mechanism allowing adults to postpone reproduction or the egg‐laying period in order to mitigate the detrimental effect of high temperatures on their probability of mating successfully or that of laying fertile eggs.     

Diapause termination and egg hatch in the bird cherry aphid, Rhopalosiphum padi

Conclusion TastePROBE is a convenient and flexible electronic circuit designed to record action potentials from taste sensilla of insects. It facilitates the recording of slow potentials arising in taste sensilla, improves the signal to noise ratio, and preserves spike shapes. This new amplifier design combines excellent signal to noise ratio with complete compatibility as regards existing electrophysiological equipment.DC recordings have higher information content than filtered recordings. With DC recordings, spike shapes are not modified and thus better sorting is possible. Moreover, slow variations in the transepithelial potential (i.e. less than 10 Hz) are preserved. Both aspects are of considerable importance when studying the physiology of taste receptors.     

The relative performance of pheromone and light traps in monitoring the seasonal activity of both sexes of the eastern hemlock looper, Lambdina fiscellaria fiscellaria

The seasonal flight activity of both sexes of the eastern hemlock looper, Lambdina fiscellaria fiscellaria Guenée (Lepidoptera: Geometridae) was studied during two consecutive years in Quebec and Newfoundland, using light (L), pheromone (P) and combined light and pheromone (LP) traps. Moth density significantly affected the performance of the different traps, with P traps being more effective at low than high density. However, P trap catches decreased just prior to the onset of female captures, probably as a result of competition between traps and virgin calling females. Nearly all females caught in L and LP traps were already mated and even the first females caught had laid at least half of their egg complement. In Quebec under warm nights, the pattern of male activity occurred at different times, with peak P catches being later in the scotophase than those of L traps, but overall similar numbers of males were caught in both traps. In contrast, under cool nights, males were caught early in the night in both P and L traps, suggesting a strong competition effect between traps, although more males were caught in P than L traps overall. In Newfoundland, the pattern of male captures in L and P traps was similar at both high and low temperatures, so competition between trap types would always be high. Under these conditions P traps were more effective than L traps. Irrespective of the region, year or temperature, significantly more males were captured in LP, with the effect of L and P being additive. In both regions, females responded similarly to L and LP traps with peak activity occurring early in the night. Captures of females were lower than those of males under cool temperatures, suggesting that the temperature threshold for flight is higher for females. The use of L and P traps simultaneously and/or in combination is discussed in relation to integrated pest management programs and ecological considerations.     

Differential effects of egg albumen content on barn swallow nestlings in relation to hatch order

In diverse animal taxa, egg mass variation mediates maternal effects with long-term consequences for offspring ontogeny and fitness. Patterns of egg mass variation with laying order differ considerably among birds, but no study has experimentally investigated the function of variation in albumen or yolk egg content in the wild. In barn swallows (Hirundo rustica), absolute and relative albumen mass increased with egg laying order. Experimental albumen removal delayed hatching, had larger negative effects on growth of late-hatched nestlings, and reduced nestling survival. Laying order positively predicted hatch order. Because nestling competitive ability depends on size, and albumen egg content influences hatchling size, present results suggest that by increasing albumen content of late eggs mothers reduce hatching asynchrony and enhance growth particularly of late-hatched nestlings. Thus, variation in albumen mass with laying order may function to mitigate the negative phenotypic consequences of hatching late in species that adopt a 'brood-survival' strategy.     

Effect of simulated fall heat waves on cold hardiness and winter survival of hemlock looper,Lambdina fiscellaria (Lepidoptera: Geometridae)

The hemlock looper (Lambdina fiscellaria) is an important pest of eastern Canadian forests. The ongoing climate warming could modify the seasonal ecology of this univoltine species that lays eggs at the end of summer and overwinters at this stage. Indeed, the increase in frequency and intensity of extreme climatic events such as fall heat waves could interfere with the winter metabolism of the hemlock looper. Moreover, the host plant quality, which influences the quantity of insect energetic reserves, the geographic origin of populations and the conditions prevailing during the cold acclimation period, could cause various responses of this pest to climate warming. The main objective of this study is to determine the impact of these factors on hemlock looper winter biology. In October 2010, hemlock looper eggs initially collected from two geographic areas in the province of Québec, and from parents reared on two host plants, were exposed to fall heat waves of different intensities during 5 consecutive days. Supercooling points and cryoprotectant levels were measured on eggs on four different dates in 2010–2011 and survival rate was measured in April 2011. Our results show that hemlock looper eggs have a very low supercooling point and high levels of trehalose, glucose and mannitol in September and November. However, there is no clear relationship between the concentration of these compounds and the decrease in supercooling points. Contents in trehalose, glucose and mannitol were significantly influenced by fall heat waves and by the origin of the population. Winter survival of eggs from the temperate population was negatively affected by strong heat waves while the boreal population was not affected. This study suggests that the metabolism and winter survival of temperate hemlock looper populations in Québec will be more affected by fall heat waves that will increase in frequency due to climate change, than boreal populations.     

Early responses of bark and wood boring beetles to an outbreak of the hemlock looper Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae) in a boreal balsam fir forest of North America

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低温和光周期对绿盲蝽越冬卵滞育解除和发育历期的影响

为了探讨温度和光周期对绿盲蝽Apolygus lucorum Meyer-Dür越冬卵滞育解除和发育历期的影响, 系统调查了绿盲蝽越冬卵在不同温度和不同光照组合下的孵化率和孵化时间, 结果显示：绿盲蝽的越冬卵均为滞育卵,低温和光周期对绿盲蝽越冬卵的滞育解除均有影响。2℃的低温处理能够显著促进其滞育解除,在0~65 d范围内,随着低温处理时间增长,其滞育解除时间缩短,未经低温处理的越冬卵T₅₀为68.5 d,低温处理65 d的T₅₀为12.25 d,绿盲蝽越冬卵在2℃低温处理65 d后完全解除滞育;在0~40 d范围内,低温处理时间越长,绿盲蝽越冬卵的孵化率越高,在25℃、全光照的条件下不经低温处理的孵化率为68.65%,低温处理40 d后在25℃的条件下的孵化率达到99.46%。在20~26℃范围内,绿盲蝽越冬卵的滞育后发育历期随着温度的上升而缩短, 随着光周期的延长而缩短。结果说明低温处理能够提高绿盲蝽越冬卵滞育解除率,但不是其滞育解除的必要条件,低温处理与自然变温对绿盲蝽滞育解除的作用相似;高温和长光照能够促进绿盲蝽的滞育解除,缩短发育历期。     

The separate effects of egg size and parental quality on the development of ornamental plumage coloration

The fitness‐related consequences of egg size, independent of the influences of parental quality, are poorly understood in altricial birds. Not only can egg size and parental quality influence growth and survival, but each could influence the development of condition‐dependent plumage coloration in offspring. The Eastern Bluebird Sialia sialis is an altricial, multi‐brooded, cavity‐nesting passerine in which juveniles display dichromatic UV‐blue plumage. Previous research suggests that plumage coloration acts as a signal of individual quality among juvenile and adult Eastern Bluebirds. Here, we separate the effects of egg size and parental quality (defined by egg size laid) on nestling growth and plumage ornamentation by exchanging clutches of large eggs with clutches of small eggs. Nestlings were significantly larger immediately post‐hatching when hatched from a large egg, but to maintain a larger size, nestlings needed to have hatched from a large egg and to have been reared by high‐quality parents. Nestlings were brighter when reared by high‐quality parents and this relationship was strongest later in the breeding season. Nestlings exhibited greater UV chroma if hatched early in the season, but UV chroma was not significantly affected by egg size or parental quality. These findings demonstrate varying influences of both egg size and parental quality on offspring growth and plumage ornamentation but suggest that quality of post‐hatching investment is more influential than pre‐hatching investment.     

Disentangling determinants of egg size in the Geometridae (Lepidoptera) using an advanced phylogenetic comparative method

We present a phylogenetic comparative study assessing the evolutionary determinants of egg size in the moth family Geometridae. These moths were found to show a strong negative allometric relationship between egg size and maternal body size. Using recently developed comparative methods based on an Ornstein-Uhlenbeck process, we show that maternal body size explains over half the variation in egg size. However, other determinants are less clear: ecological factors, previously hypothesized to affect egg size, were not found to have a considerable influence in the Geometridae. The limited role of such third factors suggests a direct causal link between egg size and body size rather than an indirect correlation mediated by some ecological factors. Notably, no large geometrid species lay small eggs. This pattern suggests that maternal body size poses a physical constraint on egg size, but within these limits, there appears to be a rather invariable selection for larger eggs.     

Effects of diapause duration on future reproduction in the cabbage beetle,Colaphellus bowringi: positive or negative?

Abstract.  Cabbage beetles, Colaphellus bowringi , undergoing an imaginal summer and winter diapause in the soil, show a great difference in diapause duration (from several months to more than 3 years) under natural conditions. The effects of diapause duration on future reproduction in the beetle are investigated at 25 °C with an LD 14 : 10 h photoperiod and under natural conditions. The fecundity of postdiapause adults with a short diapause of 5 months and nondiapause adults is similar, showing that a short diapause has no affect on reproduction, whereas the longevity of postdiapause adults with a short diapause of 5 months is significantly shorter than nondiapause adults, showing that a short diapause has a negative affect on longevity. The mean total egg production per female and longevities of postdiapause adults with long diapause periods of 16, 22, 29 and 34 months are similar to nondiapause adults, but the mean daily egg production per female is significantly higher than nondiapause adults, showing that extended diapause has a positive effect on postdiapause reproduction. The offspring of postdiapause parents require a relatively shorter time for egg development compared with the offspring of nondiapause parents, showing that diapause has a positive effect on their offspring's performance. However, there are no significant differences among offspring performance in terms of survival, adult longevity, mean egg production per female and mean daily egg production per female.     

Male influence on the duration of reproductive diapause in the large milkweed bug, Oncopeltus fasciatus

ABSTRACT. Differences were found in duration of diapause, as measured by days to first oviposition following adult eclosion, between female Oncopeltus fasciatus (Dallas) mated with male O.sandarachatus (Say) (mean =55 days), and those mated with their brothers (mean =99 days). Under the same conditions (LD 11:13 at 23°C), O.sandarachatus pairs showed no delay in reproduction (mean = 12 days). Male O.sandarachatus exhibit greater sexual activity than male O.fasciatus , and it is postulated that this behaviour may play a significant role in determining the length of diapause in the female.     

Effect of egg storage duration and brooding temperatures on chick growth,intestine morphology and nutrient transporters

The effects of egg storage duration (ESD) and brooding temperature (BT) on BW, intestine development and nutrient transporters of broiler chicks were investigated. A total of 396 chicks obtained from eggs stored at 18°C for 3 days (ESD3-18°C) or at 14°C for 14 days (ESD14-14°C) before incubation were exposed to three BTs. Temperatures were initially set at 32°C, 34°C and 30°C for control (BT-Cont), high (BT-High) and low (BT-Low) BTs, respectively. Brooding temperatures were decreased by 2°C each at days 2, 7, 14 and 21. Body weight was measured at the day of hatch, 2, 7, 14, 21, 28 and 42. Cloacal temperatures of broilers were recorded from 1 to 14 days. Intestinal morphology and gene expression levels of H⁺-dependent peptide transporter (PepT1) and Na-dependent glucose (SGLT1) were evaluated on the day of hatch and 14. Cloacal temperatures of chicks were affected by BTs from days 1 to 8, being the lowest for BT-Low chicks. BT-High resulted in the heaviest BWs at 7 days, especially for ESD14-14°C chicks. This result was consistent with longer villus and larger villus area of ESD14-14°C chicks at BT-High conditions. From 14 days to slaughter age, BT had no effect on broiler weight. ESD3-18°C chicks were heavier than ESD14-14°C chicks up to 28 days. The PepT1 and SGLT1 expression levels were significantly higher in ESD3-18°C chicks than ESD14-14°C on the day of hatch. There was significant egg storage by BT interaction for PepT1 and SGLT1 transporters at day 14. ESD14-14°C chicks had significantly higher expression of PepT1 and SGLT1 at BT-Low than those at BT-Cont. ESD14-14°C chicks upregulated PepT1 gene expression 1.15 and 1.57-fold at BT-High and BT-Low, respectively, compared with BT-Cont, whereas PepT1 expression was downregulated 0.67 and 0.62-fold in ESD3-18°C chicks at BT-High and BT-Low. These results indicated that pre-incubation egg storage conditions and BTs affected intestine morphology and PepT1 and SGLT1 nutrient transporters expression in broiler chicks.     

荔枝蒂蛀虫幼虫龄数及各发育阶段在不同温度下的发育历期

【目的】荔枝蒂蛀虫 Conopomorpha sinensis Bradley是荔枝龙眼上的主要害虫,以幼虫蛀果为害。本研究旨在明确荔枝蒂蛀虫幼虫龄数及不同温度下各虫态和各龄幼虫的发育历期,为该虫发生规律、预测预报和防控技术研究提供基础生物学数据。【方法】定期收集处于不同发育时期的荔枝蒂蛀虫幼虫,测量幼虫头壳宽度,对其进行频次分析,Crosby指数验证和曲线回归分析,以确定幼虫龄数。通过室内群体饲养的方法,测定了17~38℃区间8个温度梯度下荔枝蒂蛀虫各虫态和各龄幼虫的发育历期,并采用线性日度模型对其发育速率与温度的关系进行回归分析。【结果】根据荔枝蒂蛀虫幼虫头壳宽度频次分布图,其头壳宽度的频次分布可明显分为5个区域,说明其幼虫分5个龄期,符合Dyar定律。1-5龄幼虫的头壳宽度分别为：0.092~0.120, 0.140~0.206, 0.217~0.319, 0.356~0.523和0.582~0.728 mm。温度对荔枝蒂蛀虫卵、各龄幼虫和蛹的发育历期有明显影响,其发育历期均随温度的升高而缩短,其发育速率均与温度呈显著正相关,并符合线性回归模型。在20~32℃,荔枝蒂蛀虫可完成世代发育;在17℃时,该虫只能发育至3龄幼虫;在35℃时,蛹多不能羽化;在38℃时,卵多不能孵化。在20~32℃,其世代历期为41.16~19.34 d,蛹期为12.74~5.38 d,而产卵前期为4.75~4.22 d,温度对产卵前期无明显影响。在20~35℃,荔枝蒂蛀虫幼虫可正常发育,其1龄幼虫龄期为4.50~1.17 d,2龄幼虫期为2.09~1.40 d,3龄幼虫期为2.84~1.00 d,4龄幼虫期为3.41~1.18 d,5龄幼虫期为3.00~1.37 d,预蛹期为2.41~0.69 d。在17~35℃,荔枝蒂蛀虫卵可正常孵化,其卵期为7.73~2.09 d。【结论】荔枝蒂蛀虫幼虫分5个龄期,不同于前人所报道的4个龄期。在20~32℃温度范围内,卵、各龄幼虫和蛹的发育历期均随温度升高而缩短。本研究结果有助于荔枝蒂蛀虫预测预报方案的制定和实施。     

Effects of a host plant,Brassica juncea, on calling behaviour and egg maturation in the diamondback moth,Plutella xylostella

The influence of the presence of seedlings of a host plant, Oriental mustard,Brassica juncea (L.) Coss., on the calling behaviour and egg maturation in the diamondback moth,Plutella xylostella (L.), was investigated. In the presence of plants, females began calling at a younger age, began calling earlier in the night, and spent more time calling. Females which were kept with plants until after their first night of calling and then were isolated from plants, subsequently called less, at a level not significantly different from females which had never been exposed to plants. Of all females, both with and without plants, which were dissected at the end of the first night of calling (n=150), 93% contained mature eggs. Heavier females were significantly more likely to have mature eggs at adult emergence, to begin calling at a younger age and to spend more time calling on their first night of calling. The number of developed eggs in calling females was not significantly different in the presence or absence of host plants on the first night of calling. However, by the second night, females in the presence of plants contained significantly more eggs, indicating that the presence of plants accelerated egg maturation, both before and after the onset of calling.     

An active principle from the corpora cardiaca,corpora allata and suboesophageal ganglion of the locust,inducing egg diapause in Bombyx mori

The activity of the substance(s) which are contained in the cephalic endocrine organs of the locust which induce egg diapause in Bombyx mori was examined by implantation and injection of saline extracts of these organs. Extracts from the median and lateral neurosecretory parts of the locust brain were not effective in inducing egg diapause. Extracts of the corpora cardiaca, corpora allata, and suboesophageal ganglion of the locust induced diapause eggs in Bombyx pharate adults from which the suboesophageal ganglion had been removed. The first two extracts could induce egg diapause even in isolated abdomens of pharate adults of Bombyx. In the locust corpora cardiaca, the activity was present only in the glandular lobe and not in the nervous region. This activity decreased when the nervi corporis cardiaci I and II and of nervi corporis allati I were cut. Allatectomy also brought about a decrease in the activity in the glandular lobe which could not be restored by the injection of juvenile hormone. The activity in the corpora allata was enhanced slightly by the disconnection though not significantly.From these results, it is assumed that the corpora cardiaca, corpora allata and suboesophageal ganglion of the locust contain and active principle(s) capable of inducing egg diapause in Bombyx mori. The nervous connections between the brain, corpora cardiaca, and corpora allata are essential for the accumulation of the active substance(s) in the glandular lobes of the corpora cardiaca.     

Photoperiodic influence on the body mass of bumblebee, Bombus terrestris and its copulation duration

Abstract:  The body mass of Bombus terrestris individuals is an important trait for their behavioural performance and colony organization. In this study, colonies were reared under four different photoperiodic regimes, viz. 0 : 24, 8 : 16, 16 : 8 and 24 : 0 h light : darkness (L : D) at 28°C and 50% relative humidity. The changes in body mass were observed at the stages of larvae, pupae and on the day of adult eclosion. Both the wet and dry mass of sexuals gradually decreased with increasing day length. The relationship between body mass and copulation duration revealed that copulation duration was negatively correlated with male body mass, but positively with queen body mass. Higher number of matings by males resulted in significantly higher duration of copulation.     

Maternal influence on the incidence and duration of larval diapause in Calliphora vicina

ABSTRACT. The photoperiodic mechanism governing larval diapause in the blowfly Calliphora vicina R.-D. (Diptera: Calliphoridac) is largely maternal. The critical daylength for adult flies at 20C, and larvae derived from day 12 eggs and maintained in darkness at 11C, is about 14.5 h/24. At short daylength (LD 12:12 h) and a range of temperatures, eggs laid on or before day 9 gave rise to a low incidence of diapause, whereas those laid on day 10 and later gave rise to a high incidence; the photoperiodic 'counter' therefore shows a temperature-compensated mechanism for 'accumulating' successive short days. The rate of switching from non-diapause to diapause progeny is hardly affected by the timing of protein meals, although an early supply of meat accelerates egg development and leads to an increasing proportion of early, non-diapausing progeny. There is no evidence for a maternal effect preventing diapause induction in the first post-diapause ('spring') generation of flies. Diapausing larvae terminate diapause spontaneously in darkness at 11C after a variable period which is positively correlated with the incidence of diapause in the group. Diapause incidence and duration therefore are both determined maternally.