Summer Diapause Research Articles

Evidence for an adult summer diapause in mountain pine beetle (Coleoptera: Curculionidae) that varies geographically and among haplogroups.

Identifying dormancy traits is important for predicting insect population success, particularly in a changing climate that could disrupt evolved traits. The mountain pine beetle (Dendroctonus ponderosae Hopkins) is native to North America, is responsible for millions of acres of tree mortality, and is expanding northward in Canada. Research has identified thermal traits important to epidemic-phase ecology that vary among populations. Genomic research identified 3 mountain pine beetle haplogroups representing Pleistocene glacial refugia. Significant variation in generation timing aligning with the haplogroups has been observed. The adult stage was previously identified as the likely cause of differences among populations, although the mechanism(s) remain unclear. We tested for an adult summer diapause that varies among populations from 2 haplogroups, southern Colorado (CO) (central haplogroup) and southern Idaho (ID) (eastern haplogroup) using respirometry and reproduction experiments. Warm temperatures (25 °C) resulted in reduced respiration rates of central haplogroup mountain pine beetle compared to a cool temperature treatment (15 °C), whereas respiration of the eastern haplogroup did not differ between the treatments. Mated pairs of central haplogroup mountain pine beetle reared/held at 15 °C were more likely to be classified with a higher reproductive success rating compared to pairs reared/held at 25 °C. These results support a facultative summer adult diapause in southern CO central haplogroup mountain pine beetle. Manifestation of this diapause was low/absent among adults from the northerly ID location. This diapause likely serves to maintain univoltinism shown to be important for mountain pine beetle epidemic-phase ecology. The variation occurring among haplogroups highlights the long-term, evolved processes driving local adaptations in mountain pine beetle.

Variations in the phenological patterns of a caddisfly inhabiting the same mountain massifs: Life‐history differences in different altitudinal zones

AbstractOrganisms inhabiting mountainous regions can experience large vertical environmental changes, and show different ecological characteristics between altitudes, thus facilitating allopatric fragmentation even in geographically close populations. This study compared the life‐history patterns of a species of limnephilid caddisfly, Asynarchus sachalinensis, in several genetically differentiated populations between alpine and sub‐alpine zones in a temperate mountainous region. We showed that in the sub‐alpine populations, larval development started earlier with increasing water temperature in spring, and adult emergence was also earlier. The occurrence of adults was extremely low in mid‐summer, probably due to summer diapause, followed by a larger number of ovary‐developed females in autumn. On the other hand, in the alpine zone, increasing water temperature was delayed compared to the sub‐alpine zone, and larval development occurred from early to mid‐summer. Adult emergence and ovary‐developed individuals were concentrated in mid‐summer. Hence, summer diapause was not observed. These results indicated life‐history differences between genetically differentiated populations at different altitudes. As the timing of adult occurrence and ovarian developmental patterns differ between populations at different altitudes, it is possible that reproductive isolation is facilitated or maintained between populations.

A New Perspective to Understand the Late Season Abundance of Delia antiqua (Diptera: Anthomyiidae): A Modeling Approach for the Hot Summer Effect.

The onion maggot, Delia antiqua (Meigen), is one of the most important insect pests to agricultural crops within Allium genus, such as onions and garlic, worldwide. This study was conducted to understand the seasonal abundance of this pest, with special reference to the hot summer effect (HSE), which was incorporated into the model of summer diapause termination (SDT). We assumed that hot summer temperatures arrested the development of pupae during summer diapause. The estimated SDT curve showed that it occurred below a high-temperature limit of 22.1 °C and peaked at 16 °C. Accordingly, HSE resulted in delaying the late season fly abundance after summer, namely impacting the third generation. In Jinju, South Korea, the activity of D. antiqua was observed to cease for more than two months in the hot summer and this pattern was well described by model outputs. In the warmer Jeju Island region, Korea, the late season emergence was predicted to be greatly delayed, and D. antiqua did not exhibit a specific peak in the late season in the field. The abundance patterns observed in Korea were very different from those in countries such as the United States, Canada, and Germany. These regions are located at a much higher latitude (42° N to 53° N) than Korea (33° N to 35° N), and their HSE was less intense, showing overlapped or slightly separated second and third generation peaks. Consequently, our modeling approach for the summer diapause termination effectively explained the abundance patterns of D. antiqua in the late season. Also, the model will be useful for determining spray timing for emerging adults in late summer as onion and garlic are sown in the autumn in Korea.

On the duration of the activity period in Dermacentor reticulatus (Fabricius, 1794) (Parasitiformes, Ixodidae) ticks in the taiga zone of Western Siberia

The ixodid tick Dermacentor reticulatus (Fabricius, 1794) possesses a one-year life cycle. It is believed that adults of this species demonstrate exclusive life expectancy, can winter repeatedly, and possess a summer diapause in July. During five summer seasons, the author had tagged all the ticks collected by flagging (flag 60×120) with unrepeated marks. On the whole, 2013 tick specimens were marked. The greatest number of marked ticks was observed in the first month (319 specimens), later, from 2nd to 9th months marked ticks were collected in numbers varying from 1 to 28 specimens (16.6 ± 2.72 on average), and since 9th to 13th months, 4.5 ± 1.8 specimens. 15 ticks lived for more than a year, and the last tagged tick was collected after 463 days after the start of the experiment. Apparently, Dermacentor reticulatus are unable to winter twice in the taiga zone, because all the wintered ticks (80 specimens), according to tags, had wintered only once.

Characterization of Three Heat Shock Protein Genes in Pieris melete and Their Expression Patterns in Response to Temperature Stress and Pupal Diapause.

Simple SummaryPieris melete, a major pest of crucifers, undergoes obligatory diapause as pupae to survive unfavorable temperature extremes during hot summers and cold winters. Heat shock proteins 70 (Hsp70) participate in this process; however, little is known about the underlying changes in Hsp70 expression both during the summer and winter diapause. The study aimed to investigate expression patterns of Hsp70s (PmHsc70/PmHsp70a, b) in response to diapause and short-term temperature stresses. The results showed that the expression of PmHsc70 and PmHsp70b were upregulated both in summer and winter diapause. Heat shock significantly induced up-regulation of the three genes in both summer and winter diapause. In non-diapause pupae, none of the genes responded to cold or heat stress. Further, it was found that 39 °C for 30 min was the most sensitive heat stress condition for PmHsc70 expressions in summer diapause and all three genes’ expressions in winter diapause. During summer diapause, the expression of the genes was up-regulated in response to high temperature acclimation at 31 °C. Meanwhile, only PmHsp70a and PmHsp70b were up-regulated when acclimated to a low temperature of 4 °C in winter diapause. In conclusion, the current results indicate that PmHsp70s plays a crucial role during both summer and winter diapause, in response to temperature stresses; and our findings may contribute to the increasing knowledge on seasonal diapause adaption.Heat shock protein 70 genes participate in obligatory pupal diapause in Pieris melete to survive unfavorable conditions. In this study, three full-length cDNAs of PmHsc70, PmHsp70a and PmHsp70b were identified, and their expression patterns in response to diapause and short-term temperature stresses were investigated. Summer and winter diapause were induced in the pupae and non-diapause individuals were used as a control. The pupae from each diapause group were subjected to either hot or cold conditions and the expression levels of the HSP genes were measured. Our results showed that up-regulation of PmHsc70 and PmHsp70b were detected both in summer and winter diapause, but not for PmHsp70a. Under cold stress, PmHsp70a and PmHsp70b were upregulated in summer and winter diapause, while heat shock significantly induced upregulation of all three genes. In non-diapause pupae, none of the genes responded to cold or heat stress. Furthermore, we found that incubation at 39 °C for 30 min was the most sensitive heat stress condition for PmHsc70 expression in summer diapause. On the other hand, the same temperature was effective for PmHsc70, PmHsp70a, and PmHsp70b expression in winter diapause. During summer diapause, expression of all three genes was upregulated in response to high-temperature acclimation at 31 °C, but only PmHsp70a and PmHsp70b were upregulated when acclimated to a low temperature of 4 °C in winter diapause. These results suggest that the PmHsc70, PmHsp70a, and PmHsp70b respond differently to pupal diapause and temperature stress, and that PmHsc70 is more sensitive to heat shock than to cold stress.

A multi-year dormancy strategy in a cabbage beetle population in southeastern China.

The life cycle of the cabbage beetle Colaphellus bowringi in southeastern China is complex due to four options for adult development: summer diapause, winter diapause, prolonged diapsuse, and nondiapause. However, detailed information on the multi‐year emergence patterns of diapausing individuals in this beetle has not been documented. In this study, we monitored the adult emergence patterns of diapausing individuals and estimated the influence of the diapause‐inducing temperature and photoperiod on the incidence of prolonged diapause under seminatural conditions for several years. The duration of diapause for adults collected from the vegetable fields in different years varied from several months to 5 years. Approximately 25.9%–29.2% of individuals showed prolonged diapause (emergence more than 1 year after entering diapause) over the 5 years of observation. Furthermore, regardless of insect age, the emergence of diapausing adults from the soil always occurred between mid‐February and March in spring and between late August and mid‐October in autumn, when the host plants were available. The influence of diapause‐inducing temperatures (22, 25, and 28°C) combined with different photoperiods (L:D 12:12 h and L:D 14:10 h) on diapause duration was tested under seminatural conditions. Pairwise comparisons of diapause duration performed by the log‐rank test revealed that the low temperature of 22°C combined with the long photoperiod of L:D 14:10 h induced the longest diapause duration, whereas the low temperature of 22°C combined with the short photoperiod of L:D 12:12 h induced the highest proportion of prolonged diapause. This study indicates that C. bowringi adopts a multi‐year dormancy strategy to survive local environmental conditions and unpredictable risks.

Identification and up-regulation of three small heat shock proteins in summer and winter diapause in response to temperature stress in Pieris melete

Small heat shock proteins (sHSPs) are conserved proteins that play key roles in organismal adaptation to adversity stressors. However, little is known about sHSPs during summer diapause. Three sHSP genes: PmHSP19.5, PmHSP19.9, and PmHSP20.0 were identified and cloned from Pieris melete. Sequence alignment and phylogenetic analysis revealed that the three sHSPs have a typical, conserved α-crystallin domain. PmHSP19.5 and PmHSP20.0 were both upregulated in summer diapause (SD) and winter diapause (WD), compared to non-diapause (ND) pupae. All three sHSPs were upregulated and showed similar trends in response to thermal stress. The 0 °C chilling treatment slightly affected sHSP transcripts in ND pupae, whereas both PmHSP19.5 and PmHSP19.9 were upregulated and PmHSP20.0 was downregulated after chilling at 0 °C for 24–96 h in both SD and WD pupae. The transcripts of PmHSP19.5 and PmHSP19.9 were significantly induced at 31 °C for 30 d in SD and WD pupae. The PmHSP20.0 transcript gradually decreased during the SD and WD programs. This is the first time that sHSPs have been linked to both overwintering and summer diapause processes. These findings suggest that sHSPs are involved in both summer and winter diapause maintenance and play a possible key role in temperature stress.

CHARACTERISTICS OF THE DEVELOPMENT CYCLES OF DIURNAL LEPIDOPTERA (LEPIDOPTERA: HESPERIOIDEA, PAPILIONOIDEA) ON THE TERRITORY OF UDMURTIA

The typology of the life cycles of diurnal lepidoptera of Udmurtia is carried out using such ecological and biological indicators as the duration of generation development (number of years), the level of voltinism during the growing season, seasonal features of the imago flight, development stages at which the winter diapause occurs and its territorial confinement. On this basis, 24 types of cycles have been singled out. Species with annual development (96.7 %) and one generation during the growing season (76.4 %) are strongly predominant. According to the timing of flight, the bulavous are divided into 5 phenological groups, the proportion of which is as follows: spring - 13.8 %, pre-summer - 11.4 %, early-summer - 36.6 %, mid-summer - 35.8 %, late-summer - 2.4 %. Wintering of species is carried out at all stages of development with a predominance of larval diapause (61.5 %). Such species as Vanessa atalanta and V. cardui have the status of ex-regional migrants. The latter species is characterized by diapause-free polycyclic development throughout the year. In addition, the forms of facultative bivoltinism and summer diapause are considered.

Biology and Life Cycle of Candaharia levanderi (Simroth, 1901)

The article presents data on the biology and life cycle of Candaharia levanderi (Simroth, 1901) in laboratory and natural conditions. Candaharia levanderi belongs to the family Parmacellidae, common species in Uzbekistan. Lives for a year. On the plains in the first decade of March, it wakes up from hibernation and until mid-April, intensively feeding, prepares for reproduction. After laying eggs, the slugs die. Slugs hatched from eggs go into summer diapause. The life cycle of Candaharia levanderi consists of 4 stages: infantile, juvenile, adult and senile. Candaharia levanderi -a harmful species, the main harmfulness is high in spring. It is one of the main pests of cultivated and ornamental plants.

Modeling Climatic Influences on Three Parasitoids of Low-Density Spruce Budworm Populations. Part 3: Actia interrupta (Diptera: Tachinidae)

This article is the third and last of a series of models developed to investigate the impact of climate on the spatiotemporal biology of parasitoids. After two earlier papers investigating Tranosema rostrale and Meteorus trachynotus, this last article concerns the tachinid fly Actia interrupta (Diptera: Tachinidae). An individual-based model of the seasonal biology of A. interrupta was developed to determine the impact of climate on its interactions with two of its hosts, the spruce budworm Choristoneura fumiferana (Lepidoptera: Tortricidae) and the obliquebanded leafroller C. rosaceana in eastern North America. The model is based on the developmental responses of ‘the parasitoid’s successive life stages and the ovipositional response of adult females to temperature. It was found that the number of generations this parasitoid undergoes each year varies geographically from two to four, and that its potential growth rate, as dictated by synchrony with larvae of its overwintering host C. rosaceana, is highly patterned geographically and topographically as a result of phenological matching with larvae of obliquebanded leafroller entering diapause in late summer.

Juvenile hormone regulates the reproductive diapause through Methoprene-tolerant gene in Galeruca daurica.

Juvenile hormone (JH) signalling plays an important role in regulation of reproductive diapause in insects. However, its underlying molecular mechanism has been unclear. Methoprene-tolerant (Met), as a universal JH receptor, is involved in JH action. To gain some insight into its function in the reproductive diapause of Galeruca daurica, a serious pest on the Inner Mongolia grasslands undergoing obligatory summer diapause at the adult stage, we cloned the complete open-reading frame (ORF) sequences of Met and other 7 JH signalling-related genes, including JH acid methyltransferase (JHAMT), JH esterase (JHE), JH epoxide hydrolase (JHEH), Krüppel homologue 1 (Kr-h1), vitellogenin (Vg), forkhead box O (FOXO) and fatty acid synthase 2 (FAS2), from this species. GdMet encoded a putative protein, which contained three domains typical of the bHLH-PAS family. Expression patterns of these eight genes were developmentally regulated during adult development. Topical application of JH analogue (JHA) methoprene into the 3-day-old and 5-day-old adults induced the expression of GdMet. Silencing GdMet by RNAi inhibited the expression of JHBP, JHE, Kr-h1 and Vg, whereas promoted the FAS2 expression, which enhanced lipid accumulation and fat body development, and finally induced the adults into diapause ahead. Combining with our previous results, we conclude that JH may regulate reproductive diapause through a conserved Met-dependent pathway in G. daurica.

The remarkable biology of a new species of Gelis Thunberg, 1827 (Ichneumonidae, Phygadeuontinae), a solitary endoparasitoid of fresh eggs of Timarcha (Coleoptera, Chrysomelidae)

A new species, Gelis timarchae Schwarz, Shaw & Kan, is figured and described from specimens reared as a solitary endoparasitoid of fresh eggs of Timarcha nicaeensis in the south of France. Oviposition behaviour of the adult parasitoid, directly into the host cytoplasm, is described and links to videos are given. This appears to be the first record of any ichneumonid developing as an endoparasitoid of an insect egg, and it is a major departure from hitherto known ectoparasitoid (or spiders’ egg-predation) behaviour in the genus Gelis. Fluid from the host egg issuing from the base of the parasitoid’s ovipositor early in the oviposition process is interpreted as a necessary reduction of hydrostatic pressure before the parasitoid egg can be forced down the ovipositor. The egg and first instar larva are figured; the latter is caudate, with the caudal appendage very unusual in being bifurcate. The complex phenology and diapause of the parasitoid were investigated partly experimentally; it is broadly bivoltine with a prepupal diapause in summer, but extra generations and prolonged diapause were both also seen.

Regulation of Juvenile Hormone on Summer Diapause of Geleruca daurica and Its Pathway Analysis.

Simple SummaryDiapause is an arrestment state in development, and plays an important role in life history in insects. It has been thought that a lack in juvenile hormone (JH) results in reproductive diapause occurring at the adult stage. However, we do not fully know about the underlying molecular mechanism. In this study, we proved that the topical application of a JH analog methoprene caused the changes at the transcriptional levels of a great number of genes, inhibited lipid accumulation, and finally delayed the adults entering diapause. Therefore, JH signaling plays an important role in regulating reproductive diapause of G. daurica, a new pest with great outbreaks in Inner Mongolia.Juvenile hormone (JH) signaling plays an important role in regulation of reproductive diapause in insects. However, we have little understanding of the effect of JH on gene expression at the transcriptome level in diapause. Galeruca daurica is a new pest in the Inner Mongolia grasslands with obligatory summer diapause in the adult stage. Topical application of a JH analog methoprene at the pre-diapause stage delayed the adults entering diapause and inhibited lipid accumulation whereas it did not during diapause. Using Illumina sequencing technology and bioinformatics tools, 54 and 138 differentially expressed genes (DEGs) were detected at 1 and 2 d after treatment, respectively. The KEGG analysis showed that the DEGs were mainly enriched in the metabolism pathways. qRT-PCR analysis indicated that methoprene promoted the expression of genes encoding vitellogenin, fork head transcription factor and Krüppel homolog 1, whereas suppressed the expression of genes encoding juvenile hormone-binding protein, juvenile hormone esterase, juvenile hormone acid methyltransferase, juvenile hormone epoxide hydrolase and fatty acid synthase 2. These results indicate that JH signaling plays an important role in regulating reproductive diapause of G. daurica.

Universal and differential transcriptional regulatory pathways involved in the preparation of summer and winter diapauses in Pieris melete.

Much progress has been made in understanding the environmental and hormonal systems regulating winter diapause. However, transcriptional regulation of summer diapause is still largely unknown, making it difficult to understand an all-around regulation profile of seasonal adaptation. To bridge this gap, comparison RNA-seq to profile the transcriptome and to examine differential gene expression profiles between non-diapause, summer diapause, and winter diapause groups were performed. A total number of 113 million reads were generated and assembled into 79,117 unigenes, with 37,492 unigenes categorized into 58 functional gene ontology groups, 25 clusters of orthologous group categories, and 256 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. KEGG analysis mapped 2108 differentially expressed genes to 48 and 67 pathways for summer and winter diapauses, respectively. Enrichment statistics showed that 11 identical pathways similarly overlapped in the top 20 enriched functional groups both related to summer and winter diapauses. We also identified 35 key candidate genes for universal and differential functions related to summer and winter diapause preparation. Furthermore, we identified some genes involved in the signaling and metabolic pathways that may be the key drivers to integrate environmental signals into the summer and winter diapause preparation. The current study provided valuable insights into global molecular mechanisms underpinning diapause preparation.

Effect of photoperiod on winter and summer diapause of the soybean pod borer Leguminivora glycinivorella (Lepidoptera: Tortricidae)

• Soybean pod borer larvae continuously undergo winter and summer diapause. • Winter diapause intensity is weakened by January without photoperiodic responses. • Summer diapause is maintained by long day length. • Summer diapause ends with photoperiodic transition from long to short day length. • Males and females experiencing photoperiodic transition emerge synchronously. To understand the geographical differences between diapause systems and synchronization of adult occurrence in the soybean pod borer Leguminivora glycinivorella (Lepidoptera: Tortricidae), we examined the timing of winter diapause termination and intensity of summer diapause using univoltine and potentially bivoltine individuals in Iwate, Japan. In laboratory rearing experiments of mature larvae maintained at constant temperature (20 °C), winter diapause intensity weakened by January without photoperiodic responses. Meanwhile, summer diapause was maintained by the long day length and presumably terminated with the photoperiodic transition from long to short day length. The intensity of summer diapause was stronger for cocoons that transitioned from a 16 h light to 8 h dark (LD 16:8) to a LD 15:9 photoperiod than for those that transitioned from LD 15:9 to LD 14:10. These results suggest that populations distributed in relatively low-latitude areas, with partly or potentially bivoltine individuals, would have a weaker summer diapause or none at all. Moreover, sexual differences in the number of days to emergence were not detected when individuals experienced a photoperiodic transition from long to short day length, suggesting that the summer diapause system may function to synchronize the emergence of males and females in the population examined.

Identification and functional analysis of microRNAs in the regulation of summer diapause in Galeruca daurica

MicroRNAs (miRNAs) regulate gene expression at the post-transcriptional level. Although the regulatory roles of miRNAs in various physiological processes throughout insect development have been investigated, it is almost unknown about the roles of miRNAs involved in regulation of diapause in insects. We constructed nine small RNA libraries from Galeruca daurica adults at different diapause stages: pre-diapause (PD), diapause (D), and post-diapause (TD). Using Illumina sequencing, a total of 95.06 million valid reads was obtained, and 222 miRNAs, including 135 conserved and 87 novel miRNAs, were identified from G. daurica. The expression profiles of these miRNAs were analyzed across different diapause stages. The 30 and 13 miRNAs were differentially expressed in the D/PD and TD/D comparisons, respectively. The KEGG and GO analysis of the predicted target genes suggested the essential roles of miRNAs in the regulation of summer diapause in G. daurica, especially via the juvenile hormone, ribosome, MAPK signaling, and Ca2+ signaling pathways. Our research results indicate that miRNAs may be involved in the regulation of summer diapause in G. daurica, and these results also provide an important new small RNA genomics resource for further studies on insect diapause.

SEASONAL VARIATION OF SPIDER SPECIES COMPOSITION IN VOLGOGRAD AGGLOMERATION

The article addresses changes in the species composition of spiders during the warm season. The qualitative and quantitative characteristics of the spider community were analyzed during the most important periods of their activity in the main biotopes of the Volgograd agglomeration. The Cluster Analysis application, based on the Jaccard index, was used. The material was collected using 10 mm Barber soil traps with a fixing liquid (6% acetic acid solution). In total, 235 species of spiders belonging to 26 families were identified, including 195 species belonging to 23 families on the territory of Volgograd. Notably, 155 species were new to the fauna of the Volgograd region. Species Trichoncus villius Tanasevitch et Piterkina was found in the Russian Federation for the first time. The species composition was analyzed during critical periods of spider life: the end of winter diapause, the time before the summer diapause, the termination of summer diapause, and the period of before winter the diapause. In each case a set of traps were exposed for seven days. The spring period was characterized by the maximum number of species, and the maximum similarity in species composition was observed between the moment when spiders leave the winter diapause and the period before the summer diapause. During the warm season, the species composition changed almost completely twice: before the end of the summer diapause and at the end of the warm season, approaching the spring values. These changes were significantly less relevant to near-water biotopes, where environmental conditions were more stable compared to the other studied biotopes.

<p class="Body"><strong>Differential transcriptome profiling of the diapause and cold-responsive genes in unfed adult <em>Dermacentor silvarum</em> Olenev (Acari: Ixodidae)</strong></p><p class="Body"> </p>

The tick Dermacentor silvarum mainly overwinters in northern China as an unfed adult entering diapause; however, little is known about the involvement of genes and pathways in summer diapause and overwintering adults of this species. Hence, we investigated the differential transcriptome profile of D. silvarum ticks’ diapause and cold-responsive genes and pathways during its summer diapause, overwintering, and questing/active stages. Through transcriptomic sequencing, a total of 136,740 unigenes were assembled, and 1,549, 2,196, and 2,125 differentially expressed genes (DEG) were identified in active and diapause, diapause and overwintering, and active and overwintering ticks, respectively. Between active and diapause ticks, 875 genes were up-regulated, while 674 genes were found down-regulated in diapause ticks. When compared with active ticks, overwintering ticks had 993 up-regulated genes and 1,132 down-regulated genes. Comparison between diapause and overwintering ticks revealed 745 up-regulated and 1,451 down-regulated genes in overwintering ticks. Gene Ontology analysis revealed that, among the active, diapause, and overwintering ticks, most of the DEGs in molecular function were enriched in catalytic activity and hydrolase activity. In the cellular component, most DEGs were assigned to the integral component of the cell membrane , whereas the oxidation-reduction process was the most enriched among biological processes. In addition, the lysosome pathway was the most enriched pathway identified in KEGG pathway analysis. The above results deepened our understanding of the mechanism underlying diapause and overwintering adaptation of ticks, which is important for integrative prevention and control of ticks and tick-borne diseases.

Expression of alternative developmental pathways in the cabbage butterfly, Pieris melete and their differences in life history traits.

The seasonal life cycle of the cabbage butterfly, Pieris melete is complicated because there are three options for pupal development: summer diapause, winter diapause, and nondiapause. In the present study, we tested the influence of temperature, day length, and seasonality on the expression of alternative developmental pathways and compared the differences in life history traits between diapausing and directly developing individuals under laboratory and field conditions. The expression of developmental pathway strongly depended on temperature, day length, and seasonality. Low temperatures induced almost all individuals to enter diapause regardless of day length; relatively high temperatures combined with intermediate and longer day lengths resulted in most individuals developing without diapause in the laboratory. The field data revealed that the degree of phenotypic plasticity in relation to developmental pathway was much higher in autumn than in spring. Directly developing individuals showed shorter development times and higher growth rates than did diapausing individuals. The pupal and adult weights for both diapausing and directly developing individuals gradually decreased as rearing temperature increased, with the diapausing individuals being slightly heavier than the directly developing individuals at each temperature. Female body weight was slightly lower than male body weight. The proportional weight losses from pupa to adult were almost the same in diapausing individuals and in directly developing individuals, suggesting that diapause did not affect weight loss at metamorphosis. Our results highlight the importance of the expression of alternative developmental pathways, which not only synchronizes this butterfly's development and reproduction with the growth seasons of the host plants but also exhibits the bet‐hedging tactic against unpredictable risks due to a dynamic environment.

Summer diapause intensity influenced by parental and offspring environmental conditions in the pest mite, Halotydeus destructor

The regulation of active and dormant stages of arthropods is critical for surviving unfavourable seasonal conditions, and for many species depends on the diapause intensity (DI). There is substantial information on diapause strategies of arthropods under winter conditions; however, most cases of summer diapause are poorly understood despite its importance in most geographic regions of the world. Here we show how complex interactions with the environment drive DI involving multiple summer diapause forms of the mite Halotydeus destructor. This invasive pest in Australia is only active in cooler months but enters diapause at the egg stage which can survive hot and dry summer conditions. Recent research points to two forms of diapause egg, a typical form with a thick chorion and a cryptic form without this chorion which is morphologically similar to non-diapause eggs. Compared with typical diapause eggs which are produced in late spring, cryptic diapause eggs could be produced together with non-diapause eggs earlier in the season with relatively cooler temperatures and shorter daylength, reflecting an advanced bet-hedging strategy. Fitness trade-offs in this strategy are investigated in this study as variability of DI of the typical and cryptic diapause forms under different environmental factors for incubating diapause eggs (temperature) and rearing parental mites (different daylength, temperature and soil moisture). With the exception of daylength, all factors impacted hatchability of diapause eggs. Higher mortality of cryptic diapause eggs indicated relatively shallower DI than typical diapause eggs, likely reflecting a fitness penalty of this bet-hedging strategy under some conditions. Hatchability of cryptic diapause eggs revealed thermal and moisture stresses have opposite and complementary effects between parental and filial generations. Although DI of filial eggs decreased in hot and dry summer conditions, parental mites reared in hotter and drier conditions increased the DI of offspring. A bet-hedging strategy involving cryptic diapause might be replaced by typical diapause under consistently stressful conditions because of higher survival, regardless of additional production costs that might be required. These findings highlight a complex set of plastic responses to summer conditions in H. destructor that undoubtedly contribute to the success of this invasive pest under a range of environments.