Diapause induction and coloration in the Senegalese grasshopper, Oedaleus senegalensis

Abstract. Embryonic diapause induction in the Senegalese grasshopper, Oedaleus senegalensis Krauss (Orthoptera: Acrididae), is influenced both by the photoperiod and the temperature experienced by females. High temperatures (40°C) and long photoperiods (LD 14:10h), which characterize the beginning of the rainy season in the Sahel, cause non-diapausing eggs to be laid. Lower temperatures (25°C) and shorter photoperiods (LD 12:12h), which occur at the end of the rains, result in the production of diapausing eggs. At 30°C and constant photoperiods, O. senegalensis exhibited a long-day-short-day response with critical photoperiods of c. 13 h and c. 20 h, only the former value being of ecological significance. The photoperiodically sensitive stages to diapause induction in females occurred from the fifth stadium onwards. Temperature also affected the coloration of both nymphs and adults. Dark-black and pale-white individuals were produced by low (25°C) and high (40°C) temperatures respectively, whereas an intermediate temperature (30°C) produced individuals which were greyish brown. These results are discussed in relation to the ecology of O. senegalensis.     

The regulation of development during diapause in Ephestia elutella (Hübner) by temperature and photoperiod

Diapausing larvae of Ephestia elutella reared at 20°C in short photoperiods (LD 11:13), and then maintained 12 weeks or longer at 5–15°C before transfer to 20 or 25°C, pupated sooner than unchilled controls. At 25°C, all samples kept in long photoperiods (LD 15:9) survived better and pupated faster than similarly treated samples held in short photoperiods (LD 9:15). Samples kept at 20°C after chilling pupated much slower than those at 25°C, and, except after exposure at 5°C, pupated at similar rates at LD 11:13 or 15:9, although mortality was higher at the shorter photoperiod. After exposure at 5°C, larvae required increased day-length as well as increased temperature to hasten pupation whereas after exposure at 10°C most responded to increased temperature only.For samples maintained in slightly heated or unheated outbuildings, the summer emergence was poorly synchronized and males on average emerged ahead of females. Samples moved from the unheated outbuilding to 25°C and long days in the laboratory in early spring, however, pupated quickly and males and females emerged together. A late phase of diapause development thus exists requiring both high temperature and long photoperiods to ensure a prompt resumption of morphogenesis. Spring temperatures in the United Kingdom are seldom high enough to synchronize the completion of diapause.     

Effects of thermoperiod on photoperiodic determination of larval diapause in Ostrinia nubilalis

Some effects of thermoperiods on the photoperiodic determination of larval diapause in the European corn borer, Ostrinia nubilalis are reported. Thermoperiods and photoperiods were shown to interact to a highly significant degree in the induction of diapause. Diapause determination was found to be sensitive to the duration and temperature of the cryoscotophase of the thermophotoperiod; the thermophotophase characteristics exerted only minor influence. Cryoscotophase temperatures of 10°C or lower caused an unexpected increase in the apparent critical nightlength for diapause determination. A 0°C cryoscotophase effectively prevented the photoperiodic determination of diapause. Experimental investigation of the effects of 0°C cryoscotophases produced evidence that such low-temperature cryoscotophases may suppress the biological clock functions regulating the determination of diapause. Photoperiodic regimes in which 0°C pulses were inserted at successive points in 24-h cycle evoked responses suggesting that the early scotophase (saturation phase) was more strongly influenced by the low temperature pulse than was the later scotophase (scotonon); low temperature had little effect on the light-dependent processes (photonon) associated with the photophase.     

Under-sized larvae from short-day adults of the blow fly, Calliphora vicina, side-step the diapause programme

Abstract. Larvae of Calliphora vicina R.-D. (Diptera: Calliphoridae) hatching from eggs laid by adult females exposed to short day length, and then raised in darkness at 11^oC, normally enter diapause rather than undergoing prompt pupariation. However, if the feeding stage is curtailed by premature extraction of larvae from their food, or if the larvae are subjected to severe overcrowding, smaller larvae side-step the diapause programme to become miniature puparia, whereas larger larvae proceed to diapause as fully-fed ones. In addition, smaller diapausing larvae show a shorter (or less intense) diapause than full-sized larvae. Apart from the smallest individuals, flies can emerge from these miniature puparia and in some cases are capable of laying eggs; this suggests that avoidance of diapause may allow undersized individuals an opportunity to reproduce before winter sets in. Fat determinations performed on larvae and pupae of various sizes, however, showed that short-day (diapause-destined) individuals lay down the same proportion of fat as long-day (non-diapause) individuals, and the same proportion of fat across all size classes. The possible functional significance of this phenomenon is discussed.     

Geographic variation in critical photoperiod for diapause induction and its temperature dependence in Hyphantria cunea Drury (Lepidoptera: Arctiidae)

The fall webworm, Hyphantria cunea Drury (Lepidoptera: Arctiidae), was introduced from North America to Japan half a century ago. The critical photoperiod for diapause induction and its temperature dependence, as defined by the difference in the critical photoperiod between 20 and 25°C, were investigated in order to understand the mechanisms behind a shift from bi- to trivoltine life cycles. The critical photoperiod for diapause induction was shorter in the southern trivoltine populations than in the northern bivoltine populations, and this was more marked at 25°C than at 20°C. Although the critical photoperiod showed a positive correlation with the original latitude, the correlation was relatively low at both temperatures. Conversely, temperature dependence of the critical photoperiod for diapause induction correlated negatively with the original latitude. The trivoltine populations showed greater temperature sensitivity than the bivoltine populations. These results suggest that an increase in temperature sensitivity of the diapause response to photoperiods was involved in the shift to a trivoltine life cycle. The crossing experiments suggested that the photoperiodic control of diapause induction and its temperature dependence are under polygenic control without sex-linkage. Received: 29 October 1996 / Accepted: 26 February 1997     

Temperature and photoperiodic control of diapase induction in the ant <Emphasis Type="Italic">Lepisiota semenovi</Emphasis> (Hymenoptera,formicidae) from Turkmenistan

The ants L. semenovi has been found to belong to species with endogenous-heterodynamic seasonal life cycles with the obligate diapause induced predominantly by factors internal for a colony, whereas external ecological factors (photoperiods and temperature) produce merely modifying effects by accelerating or delaying the diapause onset. The photoperiodic and temperature regulation of diapause induction in larvae and queens is shown. Under effect of short days and low temperature the periods of larval pupation and queen oviposition in a colony are shortened markedly, i.e., the diapause of larvae and queens occurs earlier. The daily rhythms of temperature 15/25°C and particularly 20/30°C as compared with constant temperatures 20 and 25°C that correspond to the mean circadian temperatures of the thermorhythm, inhibit manifestations of the short day effects by stimulating the non-diapause development and increasing duration of the seasonal development cycle of ant colonies. The L. semenovi photoperiodic reaction is quantitative, as development and pupation of larvae and egg-laying of queens cease sooner or later under both the short and the long days, but in the latter case significantly later. Thus L. semenovi is one more example among very rare ant species that are revealed to have the photoperiodic regulation of the colony development seasonal cycle.     

ASSOCIATION BETWEEN LATITUDINAL VARIATION FOR EMBRYONIC DEVELOPMENT TIME AND CHROMOSOME STRUCTURE IN THE GRASSHOPPER CALEDIA CAPTIVA (ORTHOPTERA: ACRIDIDAE)

From southeastern Queensland to southern Victoria, over a transect of 11° latitude, the Moreton taxon of the Australian grasshopper Caledia captiva exhibits a cline in chromosome structure that involves change from a metacentric to an acrocentric genome. In this study, we show that embryonic development time covaries with chromosome structure along the transect. Both development time and chromosome short arm length exhibit an overall negative correlation with latitude, but with maxima just south of the northern limit of the taxon's distribution. Selection for such a pattern appears to arise from changes in voltinism along the cline in season length that exists along the transect. Populations with the highest temperature thresholds for avoidance of embryonic diapause also have the slowest development time and probably represent the northern extreme of a primarily univoltine life cycle. North of this region bivoltinism increases in frequency and, as expected from a split of the season length, development time decreases. Maximum chromosome short arm length occurs in the vicinity of the northern univoltine populations, rather than at the limit of distribution where bivoltinism prevails. We conclude that variation in chromosome structure could be contributing to the heritable variation for development time that forms the basis for adaptive change in this trait. These results provide justification for investigating causal relationships between chromosome structure and development time, with an ultimate aim of understanding the adaptive significance of chromosomal variation in C. captiva.     

Photoperiodic effect on size-related metamorphosis in the milkweed leaf beetle, Labidomera clivicollis

ABSTRACT. Photoperiod significantly affected size-related aspects of metamorphosis in the milkweed leaf beetle Labidomera clivicollis (Kirby) (Chrysomelidae). Larvae reared under short-day photoperiod successfully pupated at lower weights than larvae reared under long-day photoperiods. This short-day effect was observed to an equivalent extent in both males and females; but within photoperiod treatments, males consistently pupated at lower weights than females. It is likely that the short-day effect on metamorphosis is associated with photo-periodically induced changes in larval corpora allata activity or juvenile hormone titre. Ecologically, the short-day effect on metamorphosis may enhance the moulting success of larvae which encounter food shortages during autumn.     

Diapause induction in the oblique-banded leafroller Choristoneura rosaceana (Lepidoptera: Tortricidae): Role of photoperiod and temperature

Induction of diapause in the larval stage of the oblique-banded leafroller, Choristoneura rosaceana (Harris), was found to be dependent on both photoperiod and temperature. At constant temperatures of 24, 20 and 16°C, short photoperiods induced diapause. The critical photoperiod was between 14–15 h of light per day at 20 and 16°C. At 14 h light: 10 h dark, all larvae expressed diapause. Temperature had a modifying effect, and slightly shifted the larval response to diapause-inducing photoperiods. High constant temperatures of 28°C and above induced diapause in some individuals (< 20%), while fluctuating temperatures of 32 and 16°C in a 12-h cycle resulted in 67% diapause induction, suggesting that diapause could also be induced by fluctuating temperatures, particularly if the higher temperature exceeds 25°C.The first- and the second-instar larvae were the only two stages sensitive to diapause induction. Exposure of adult, egg and third, fourth, and fifth-larval instars to diapause-inducing conditions did not produce diapause. Although diapause was induced in the first or the second instars, it was always expressed in the third or fourth instar.     

Life history of Galerucella nymphaeae and implications of reproductive diapause for rearing univoltine chrysomelids

Abstract. Galerucella nymphaeae L. , a chrysomelid that feeds on Lythrum spp., water lily and water chestnut, is closely related to two European species that were recently introduced into North America for biological control of L.salicaria , purple loosestrife. To develop a paradigm for continuously rearing these and other univoltine chrysomelids, we conducted field and laboratory studies on G. nymphaeae's development , reproduction and diapause.
A high incidence of reproduction without diapause occurred when fourth instars, pupae, and adults (held as pairs) experienced very long daylengths (LD18:6 h), i.e. longer than those G.nymphaeae encounters in nature. Under similar photoperiodic conditions, adults maintained in groups showed a significantly higher rate of reproductive diapause than those held as pairs. Females laid three to seven egg masses/week, and the size of egg masses varied between nine and nineteen eggs. During their reproductive lifetimes, individual females showed a highly significant propensity to lay a consistent number of eggs/egg mass.
After diapausing under short daylengths and low temperature (LD 10:14h, 5C), adults transferred to long days (LD 18:6h at 21C) had high rates of diapause termination and postdiapause oviposition. In contrast, those transferred to short daylengths (LD 10:14h at 21C) had low rates of reproduction.
Laboratory-derived heat-degree models accurately predicted egg and pupal, but not larval, development in the field. In nature, most females in the summer generation entered reproductive diapause without ovipositing; a small proportion of females that emerged relatively early (by mid June) oviposited before entering diapause. The overwintering population consists of adults from the first-generation and a small number from the second generation.     

光周期对内蒙古三种草原蝗虫高龄若虫发育、存活、羽化、生殖的影响

研究不同光周期(L8∶D16、L12∶D12及L16∶D8)对毛足棒角蝗Dasyhippus barbipes(F.-W.),亚洲小车蝗Oedaleus decorus asiaticus B.-Bidenko,小翅雏蝗Chorthippus fallax(Zub.)3种草原蝗虫高龄若虫的发育、存活、羽化、生殖的影响。结果表明:在白天温度(28±1)℃,黑夜温度(23±1)℃的恒定温度下,不同光周期对毛足棒角蝗和亚洲小车蝗高龄若虫的发育、羽化、产卵影响不大,但是对其存活率有极显著的影响:毛足棒角蝗和亚洲小车蝗高龄若虫到成虫的发育速度在中光照下(L12∶D12)最快。而在短光照(L8∶D16)下更有利于小翅雏蝗若虫发育,其次是中光照;毛足棒角蝗的羽化在中光照条件下最适宜,而长光照时数(L16∶D8)更有利于亚洲小车蝗和小翅雏蝗的羽化;光周期对亚洲小车蝗产卵影响最为明显,毛足棒角蝗和亚洲小车蝗在中光照和长光照时数条件下有利于它们产卵,而小翅雏蝗在短光照和中光照时数下有利于产卵。     

Seasonal occurrence and diapause induction of a predatory bug Andrallus spinidens (F.) (Heteroptera: Pentatomidae)

The bug Andrallus spinidens (F.) (Heteroptera: Pentatomidae) is a polyphagous predator of insect larvae, which is distributed in tropical and warm temperate zones worldwide. Seasonal occurrence and diapause induction of this bug were studied in a population in Miyazaki, southern Kyushu, Japan. The field research showed that A. spinidens produces three or four generations a year and is most abundant from mid‐summer to autumn. Reproductive activity of field‐collected adults decreased from late summer to autumn, indicating that this bug enters adult diapause in autumn. Only adults were found in early spring and these were reproductive. Laboratory experiments showed that, irrespective of photoperiod, adult diapause is induced at lower temperatures (≤22.5°C), whereas it is avoided at higher temperatures (≥25°C). Ambient temperature falls across the critical range from late summer to autumn. Thus, the bug clearly overwinters in adult diapause induced by low temperatures and this diapause is terminated during the course of winter.