Induction of winged sexuparae in root-inhabiting colonies of the aphid Pemphigus betae

Abstract. Growth chamber experiments were conducted to determine what environmental factors induce the development of sexuparae in root-feeding colonies of the aphid Pemphigus betae Doane (Aphididae: Pemphiginae). Experimental colonies were derived from clones that had been reproducing for at least 15 months under constant laboratory conditions. At constant 20–23^oC, sexuparae were almost never produced regardless of the level of crowding or photoperiod. In contrast, every culture of several clones produced sexuparae when subjected to temperatures alternating between 20 and 15^oC during the light and dark phases respectively. This fluctuating temperature regime resulted in sexupara production regardless of photoperiod. All cultures also produced some sexuparae when cultures were kept in constant darkness at temperatures that were either alternated between 20 and 15^oC or kept constant at 15^oC. Constant 17^oC resulted in sexupara production in most cultures. At 17^oC, experimental manipulation of densities within cultures showed that crowding promotes sexupara production. Thus, within the range of conditions occurring at the time of sexupara induction in the field, photoperiod has no effect on sexupara production, temperature below a threshold between 17 and 20–23^oC triggers sexupara production, and crowding promotes sexupara production but only if temperature is low enough.     

The inhibition of vegetative cell outgrowth and division from spores of Bacillus cereus T by hen egg albumen

Spores of Bacillus cereus T germinated and formed vegetative cells in Tryptone Soya broth (TSB), pH 9-0 and 7-4 at 30^oC. Spores germinated but did not form vegetative cells when suspended in hen egg white (pH 9-0) supplemented with L-alanine and inosine. Using a split image eyepiece, the volumes of germinating spores in egg white were seen to increase as a result of increases in both length and breadth. In TSB at the same pH, the major volume increase resulted from a progressive increase in cell length. Egg white supplemented with L-alanine and inosine (pH 7-6 30^oC) allowed limited outgrowth to occur but the vegetative cells differed in morphology to those in TSB. Fe(NH₄)₂(SO₄)2.6H₂O overcame the inhibition of outgrowth in egg white at pH 7–8 but not in egg white at pH 9-1. Solutions containing trace elements, growth factors and casamino acids could not replace iron in this respect. Sporulation occurred in egg white only when iron was present.     

Thermal response and reversibility of diapause in the eggs of Locusta migratoria

Abstract. Eggs of a local population of Locusta migratoria L. (Orthoptera: Acrididae) collected near Hirosaki (40.5^oN) entered diapause when incubated at temperatures between 20 and 35^oC. For diapause development the optimum temperature was 10^oC. The lower thermal threshold for post-diapause development was 14.7^oC. After chilling at 10^oC for 20 days, the rate of hatching varied with incubation temperature, being 0, 61% and 81% at 20, 25 and 30^oC, respectively. After chilling for 40 days or more, however, almost all eggs hatched at 20–30^oC. Diapause with a reduced intensity seemed to be eliminated easily by a high temperature of 25 or 30^oC.
When eggs chilled at 10^oC for 20 days were kept at 20^oC for 7 days or more before incubation at 25^oC, almost all eggs maintained diapause. Most eggs chilled at 10^oC for three 10 day periods separated by 3 days of warming at 25^oC failed to terminate diapause. Daily alternations of 10^oC (18 h) and 25^oC (6h) decreased the diapause-terminating effect of chilling. These facts suggest that diapause intensity can be restored if eggs chilled insufficiently are exposed to a moderately high temperature. This reversible change in diapause intensity would play an important role in maintaining diapause before winter.     

Energetics and foraging behaviour of the European seed harvesting ant Messor capitatus: I. Respiratory metabolism and energy consumption of unloaded and loaded workers during locomotion

Abstract The respiratory metabolism of workers of Messor capitatus (Latreille) was measured using standard micro-Warburg techniques on single individuals. The experiments were carried out at 10, 20, 25, 30 and 40^oC, and the respiratory quotient (RQ), measured for the same individuals at 30^oC, was found to be 0.77. The specific respiratory rate (y , in μl O₂/mg dry weight/h) could be described by the following equation: Iny = -2.24 + 0.098r -0.258 In W; where T is temperature and W is the dry weight in mg. The Q₁₀ for M. capitatus in the temperature interval 20–30^oC was 3.4, a higher value than for other ants.
The energy costs of movement and carrying were determined by using the RQ to convert the continuous measurement of CO₂ produced at 30^oC by Enfiuran anaesthetized workers ('resting metabolism'), by running workers and by workers loaded with a 20 mg weight to units of energy. The resting metabolism was 10.0±1.0 mJ/mg fresh weight/h. The cost of running ( Y in joule per km) could be described by: Y = 3.865 + 0.363 Wf , where Wf is fresh weight in mg. The cost of transport for all experiments could be expressed as 0.64 × the cost of running.     

Calling behaviour in M.convecta females under different temperature and photoperiodic conditions

Abstract. . The effects of temperature and photoperiod on calling behaviour in females of the Australian common armyworm, Mythimna corwecta (Walker) (Lepidoptera: Noctuidae), were studied in the laboratory. Age at first calling was greater at 15 and 20^oC compared with 25^oC, but there were no significant differences between 25 and 30^oC. Females kept at 10^oC did not call, but if transferred at 10 days to 20^oC they called after a period similar to the pre-calling period at constant 20^oC. Onset time of calling was earlier at 15 and 20^oC compared with 25 and 30^oC, but there were no significant differences in calling duration. At 20^oC, age at first calling was increased by shorter day length (12h and 14h, compared with 16h), and there was an interaction between daylength and moth age affecting the duration of calling. Onset times advanced with longer daylength, but peak calling was later in relation to the lengtii of the scotophase. These results are discussed in connection with migration in M.convecta. Evidence for a circadian rhythm of calling was found in females entrained for 3 and 8 days after emergence under reverse-cycle conditions and then transferred to constant darkness. However, after 56 h and 80 h respectively of darkness, calling became de-synchronized. Subsequently, it appeared to re-synchronize to a different clock, which approximately correlated with the normal photoperiods the moths had experienced during larval development.     

Cold shock and heat shock: a comparison of the protection generated by brief pretreatment at less severe temperatures

Abstract Brief exposure to low (0^oC) or high (40^oC) temperature elicits a protective response that prevents injury when the flesh fly, Sarcophaga crassipalpis Macquart, is subjected to more severe cold (-10^oC) or heat (45^oC). Both the low and high temperature responses were found in all developmental stages of the fly, but were most pronounced in the pupal and pharate adult stages. The protective responses generated by brief exposure to 0 or 40^oC appear similar in that both result in a rapid acquisition of cold or heat tolerance and a loss of protection after the flies are returned to 25^oC. The protection generated by chilling is obvious within 10 min of exposure to 0^oC while a 30 min exposure to 40^oC is required to induce the high temperature protection. High temperature protects against cold shock injury within a narrow range (around 36^oC) but we have no evidence that low temperature can protect against heat injury. We previously demonstrated that the rapid increase in cold tolerance correlates with concomitant increases in glycerol concentration, but in this study we found no significant elevation in glycerol in heat-shocked flies. Thus the physiological and biochemical bases for the rapid responses to cold and heat appear to be different.     

Temperature-dependent development and survival of the lesser mealworm, Alphitobius diaperinus

Abstract. Development, growth and survival of the lesser mealworm, Alphitobius diaperinus (Panzer), were determined at six constant temperatures. No egg hatch or larval development occurred at 17^oC. At temperatures of 20, 25, 30, 35 and 38^oC the median development times (days), respectively, were for eggs (13.4, 6.0, 4.4, 2.6 and 2.6), larvae (133.0, 46.0, 26.2, 22.4 and 23.9), pupae (17.0, 8.0, 5.5, 4.0 and 4.1), and from oviposition to adult emergence (164.4, 60.2, 37.9, 29.0 and 30.8). The Sharpe & DeMichele (1977) model was used to describe the temperature-dependent development. The mean egg survival (hatching) ranged from 61% to 86%, with lowest hatch at 20^oC. Survival of the larvae and pupae ranged from 32% to 73% and from 85% to 95%, respectively, with lowest survival at 20^oC. Pupae had significantly lower weights at 35^oC and adults at 38^oC than at the other temperatures. Female pupae (20 mg) and female adults (16 mg) were significantly heavier than male pupae (17 mg) and male adults (13 mg). Adults (0.5–9 months old) laid 4–7 eggs per female per day at 25^oC.     

Studies on the survival and transmission of Xanthomonas manihotis on cassava seed

Cassava seed which had been stored at 5 ^oC and 60% r.h. for 2–51 months was assayed for the presence of Xanthomonas manihotis by a leaf-infiltration technique, using as inoculum the supernatant from seeds soaked in sterile water at 30 ^oC for 2–4 h. The threshold of sensitivity of the assay method was 10⁵ cells/ml. Twenty out of 50 samples yielded the pathogen. The infested seed had been in storage for 2–18 months. Bacteria reisolated from infiltrated leaves were identical to X. manihotis in cultural characteristics, phage type and pathogenicity. Surface sterilisation or hot air treatment for 24 h at 65^oC or lower did not eliminate the pathogen from infested seed. Soaking of infested seed in hot water at 60 ^oC for 20 min reduced the number of bacteria to less than the minimum detectable level without appreciably reducing germination. Cassava bacterial blight was observed in 8-wk-old seedlings which had been planted during the dry season at a site where infection from outside sources was unlikely. It is postulated that a low percentage of successful seed transmissions of X. manihotis can occur under favourable environmental conditions.     

A mutant strain of Chymomyza costata (Diptera: Drosophilidae) insensitive to diapause-inducing action of photoperiod

ABSTRACT. From a Japanese population of Chymomyza costata which has been known to have a photoperiodic larval diapause, we selected a mutant strain which did not respond to photoperiod. However, about 70% of the individuals of this strain entered diapause at 11^oC irrespective of photoperiod, and about the same percentage of those of the photoperiod-sensitive strain also did so in continuous illumination at 11^oC. This indicates that low temperature induces diapause independently of photoperiod. On the other hand, a temperature drop from 18 or 25^oC to 15^oC and chilling at 4^oC did not induce diapause.     

The effect of temperature and inoculation access period on the transmission of barley yellow dwarf virus byRhopalosiphum padi (L.) and Sitobion avenae (F.)

Winged individuals of Rhopalosiphum padi and Sitobion avenae transmitted the PAV-like and MAV-like isolates of barley yellow dwarf virus respectively. Success of transmission after inoculation access periods of 2, 6, 12, 24, 48 and 72 h were examined and survival, reproduction and movement of the aphid vectors were recorded at these times. The experiment was done at four different temperatures: 6^oC, 12^oC, 18^oC and 23^oC. For both isolates the inoculation efficacy did not increase after a 24 h inoculation access period and there was no difference in inoculation efficiency at the three highest temperatures, that at 6^oC being significantly lower than at 12^oC to 23^oC. The results suggest that autumn temperature is a critical factor for BYDV epidemiology in Britain with a small increase in autumn temperature leading to greatly increased infection rates.     

Effects of temperature on virogenesis of bluetongue virus serotype 11 in Culicoides variipennis sonorensis

Abstract. Culicoides variipennis sonorensis females were fed bluetongue virus serotype 11 mixed in sheep blood and were held at constant temperatures of 32, 27, 21 and 15^oC. Virogenesis, as measured by enzyme-linked immunosorbent assay (ELISA), proceeded significantly faster at higher temperatures. Based on ELISA absorbance ≥0.2, some flies first were categorized as infected after 1 day, 2 days and 4 days at 32, 27 and 21^oC, respectively. Peak levels of virus antigen were seen after 5–7, 7–13 and 18–22 days for flies held at 32, 27 and 21^oC, respectively. There was no significant virus replication in flies held at 15^oC for 22 days, but latent virus replicated and was detected easily (44% infection) 4–10 days after these flies were transferred to 27^oC. The implications for temperature effects on bluetongue epizootiology are discussed.     

Effects of temperature on development of Otiorrhynchus sulcatus (Coleoptera: Curculionidae)

Development of the black vine weevil, Otiorrhynchus sulcatus , was investigated at constant temperatures from 9 to 27 ^oC. Pre-adult development was completed in 200 and 130 days at 15 and 24 ^oC, respectively. Eggs and larvae developed at 27 ^oC, but no pupation took place at this temperature. The developmental threshold temperatures for eggs, larvae + pre-pupae and pupae were 6, 2–6 and 12 ^oC, respectively. Reproductive maturation of females took place at temperatures from 12 to 27 ^oC, but only a few females became reproductive at 12 ^oC. Most females at 12 ^oC, like those at 9 ^oC, had a short maturation feed, but the ovaries did not develop. The pre-oviposition period was temperature dependent. The females showed a cyclic oviposition pattern with three peaks. The significance of soil temperatures for the phenology and distribution of O. sulcatus in Norway is discussed.     

Assessment of phosphine fumigation as a plant quarantine measure against Spodoptera littoralis

In laboratory tests first instar larvae of Spodoptera littoralis were killed by phosphine fumigations of 24 and 48 h at a concentration x time product (CTP) of 36 mg h/1. Eggs aged 1–2 days were, however, tolerant to phosphine at a CTP of 144 mg h/1 and this CTP caused severe damage to chrysanthemum cuttings (cv. Freedom). When eggs aged < 1 day and 1–2 days old were preconditioned at 20 ^oC for 72 h before phosphine fumigation, complete mortality occurred at CTPs at and above 36 mg h/1. Preconditioning for 48 h at 20 ^oC and for 48 and 72 h at 15 ^oC did not produce 100% mortality at a CTP of 288 mg h/1. It was suggested that eggs of S. littoralis pass through a phase of tolerance to phosphine which at 20 ^oC lasts about 4 days after oviposition.
There was no indication that phosphine was toxic to chrysanthemum cuttings (cv. Pollyanne) at concentrations of 0–75 mg/1 (CTPs of 18 and 36 mg h/1). Storage at 15 ^oC was not damaging to cuttings but at 20 ^oC some damage became apparent.     

Evaluation of a monoclonal antibody-based immunoassay for detecting type A Clostridium botulinum toxin produced in pure culture and an inoculated model cured meat system

A monoclonal antibody-based amplified enzyme-linked immunosorbent assay (ELISA) method for detecting Clostridium botulinum type A toxin was evaluated for its ability to detect the toxin in the supernatant fluid of pure cultures and after growth from Cl. botulinum spores inoculated into pork slurries. Slurries containing NaCl (1.5-4.5% w/v) and polyphosphate (0.3% w/v) were either unheated or heated, 80 degrees C/5 min + 70 degrees C/2 h, before storage at 15 degrees, 20 degrees or 27 degrees C. The presence of specific toxin was confirmed by mouse bioassay and results compared with those of the amplified ELISA method. A total of 49 strains, 39 Cl. botulinum and 10 Cl. sporogenes (putrefactive anaerobes), and 95 slurry samples were tested. Fourteen of 15 strains of type A Cl. botulinum and 34 of 36 slurry samples containing type A toxin were positive by ELISA. No false positive reactions occurred with Cl. botulinum types B, C, D, E and F, or with the 10 strains of Cl. sporogenes. However, toxin produced by one strain of Cl. botulinum type A (NCTC 2012) was not detected by the amplified ELISA.     

A note on the performance of Rappaport's medium, compared with Rappaport-Vassiliadis broth, in the isolation of salmonellas from meat products, after pre-enrichment

Salmonellas were isolated from meat products using a slightly modified Rappaport's enrichment medium (R25), Rappaport-Vassiliadis procedure (Rappaport's broth containing 10 ml instead of 30 ml of Malachite Green solution and incubated at 43^oC instead of 37^oC), and Muller-Kauffmann's tetrathionate broth. From 255 samples, 89 were found positive with the Rappaport-Vassiliadis procedure, 83 with the R25 broth, whereas only 43 were positive with Muller-Kauffmann broth. It is concluded that the R25 medium may be used as an alternative to the more effective Rappaport-Vassiliadis broth when the only available incubation temperature is 37^oC.     

Life span and ovarian dynamics of the pine beauty moth, Panolis flammea (D&S): the effect of low temperatures after adult emergence on reproductive success

Abstract Adult female Panolis flammea were kept at 2^oC either immediately after emergence from the pupae or immediately after mating, for periods ranging from 5 to 20 days and then placed at 15^oC together with a male moth, food supply and suitable oviposition site ( Pinus contorta foliage). Weight loss over the storage period was directly proportional to the time spent at 2^oC irrespective of whether the moths were virgin or mated. Pre-oviposition period decreased significantly from the control after more than 5 days at 2^oC, but there was no significant difference between late mated and early mated moths. The post-storage life span of late mated and early mated moths decreased in proportion to the time spent at 2^oC but late mated moths had significantly longer life spans than early mated moths. Moths mated prior to storage were significantly less fecund than moths mated after storage except those moths kept at 2^oC for 20 days where the fecundities of both treatments were identical (c. 45 eggs/female). These results are discussed in relation to the conditions likely to be experienced by P.flammea in the field and their bearing on the population dynamics of this insect.     

The potential for control of the blowfly Lucilia sericata using odour-baited targets

Abstract A deterministic simulation model is used to explore the potential for control of the sheep blowfly, Lucilia sericata , using odour-baited targets. The simulations show that the ambient temperatures of 15^oC or 20^oC, 13% and 24% of the females present in a population would need to be killed per day, respectively, to prevent the population growing from its initial spring density during the summer blowfly season. In contrast, if both sexes could be sterilized, so that sterilized males were also able to disrupt the fertility of unsterilized females, only 6.5–13% of both sexes would need to be attracted and sterilized at 15^oC or 20^oC respectively. To examine whether these numbers of individuals could be attracted by targets baited with liver and sodium sulphide, mark-release-recapture studies in sheep pastures were used to quantify sticky target efficiencies. The percentage of the Lsericata population caught on any one day was shown to be positively related to average ambient temperature. At 15^oC each sticky target caught approximately 13% and at 20^oC, 41% of the females within a 20 m radius. The results indicate that, at ambient temperatures between 15 and 20^oC, if distributed at a density of approximately 5/ha, targets baited with liver and sodium sulphide could effectively suppress a population of L.sericata. Lower densities of targets would be required if they were able to sterilize both sexes rather than kill or if more attractive synthetic semiochemical baits could be developed.     

Evaluation of a monoclonal antibody-based immunoassay for detecting type B Clostridium botulinum toxin produced in pure culture and an inoculated model cured meat system

A monoclonal antibody-based amplified ELISA method for detecting Clostridium botulinum type B toxin was evaluated for its ability to detect the toxin in the supernatant fluid of pure cultures and after growth from Cl. botulinum spores inoculated into pork slurries. Slurries containing NaCl (1.5–4.5%w/v) and polyphosphate (0.3%w/v) were either unheated or heated 80°C/5 min followed by 70°C/2 h before incubation at 15°, 20° or 27°C. Presence of specific toxin was confirmed by mouse bioassay and results were compared with those of the amplified ELISA method. A total of 48 strains, consisting of 38 Cl. botulinum and 10 Cl. sporogenes (putrefactive anaerobes), and 140 slurry samples were tested. Cultures of eight out of nine strains of type B Cl. botulinum and 73 of 101 slurry samples containing type B toxin were positive by ELISA; the remaining 28 slurry samples contained type B toxin at levels below or close to the detection limit (20 LD₅₀/ml) of the type B ELISA. No falsepositive reactions occurred with Cl. botulinum types A, C, D, E or F, or with the 10 strains of Cl. sporogenes. Toxin produced by one strain of Cl. botulinum type B (NCTC 3807) was not detected by this single monoclonal antibody-based amplified ELISA. With a mixture of two monoclonal antibodies, however, the toxin from NCTC 3807 could be detected without reducing the sensitivity of the ELISA.     

Inhibition by Botulinum Toxin of Acetylcholine Release from Synaptosomes: Latency of Action and the Role of Gangliosides

Abstract: Crude and crystalline botulinum toxin type A have been compared for their ability to inhibit [¹⁴C]ACh release from synaptosomes preloaded with [¹⁴C]choline. The toxin preparations exhibited similar dose-response curves, with maximal inhibition at 10⁵ mouse LD₅₀/ml after 60 min preincubation. The time course for the inhibitory action of the toxin showed that inhibition develops almost linearly over this time period. However, free toxin could be removed from the synaptosome suspension after 15 min without altering the subsequent development of inhibition of [¹⁴C]ACh release, which suggests that the toxin is rapidly fixed by synaptosomes and that fixation alone cannot account for the latency of its action. Incorporation of gangliosides into synaptosomes by prior preincubation failed to increase the potency of the toxin, which implies that gangliosides do not serve as the membrane receptor for the toxin. Treatment of botulinum toxin with dithiothreitol greatly diminished its ability to inhibit [¹⁴C]ACh release and it is suggested that botulinum toxin may be analogous to other bacterial toxins in its structure and mode of action.     

Development rates of some pre-adult stages in blowflies with reference to low temperatures

Abstract. Duration of some pre-adult stages of Calliphora vicina Robineau-Desvoidy, C.alpina Zett., C.vomitoria Linn., Phormia terraenovae R.-D. and Lucilia sericata Meig. were determined at 3.5–26^oC, in the context of use of these insects in forensic estimates of post-mortem intervals. Egg development in C. vicina occurs down to at least 3.5^oC, larval growth to 4^oC and puparial formation, development and perfect adult emergence to 5^oC. Growth curves by successive weighing of individual larvae showed specific differences in rates of development of the above species at constant temperatures. Alternating temperatures for 12 h periods (such as 10^oC and 20^oC) to simulate diurnal changes, usually, but not at all temperature pairs tested, caused acceleration of growth relative to the corresponding constant temperature (15^oC in the above case), in C.vomitoria, P.terraenovae and L.sericata , but usually caused retardation of larval growth in C.vicina. In this species, larvae as single individuals on beef liver in small tubes grew on average at the same rates as those (50–100 larvae) growing communally. All species showed variation in larval growth between individuals, more marked in C.vicina , and slower-growing larvae showed increased unexplained mortality. Because of this and to avoid complication by fast-growing larvae from later laid egg batches on a carcass, growth curves given are those of mean weights of the heaviest 25% (upper quartile) of groups of 40–90 feeding larvae. Variation in growth rates, and acceleration or retardation of growth in different species under alternating temperatures, thus affect suggested procedures in obtaining estimates of post-mortem intervals using these insects.