Biology, life table and host specificity of the mushroom pest, Brennandania lambi (Acari: Pygmephoroidea)

Biology and life table parameters of Brennandania lambi (Krczal) were studied at different temperatures while feeding on white mushroom (Agaricus bisporus) mycelium cultured on mushroom compost. The duration of egg and larva development, preoviposition and oviposition period, female longevity, and the time to 50% mortality declined as temperature increased from 16 to 28°C. The threshold temperature of development (female) was 9°C and the thermal constant for completion of development (female) was 195 day-degrees. At 16, 20, 24 and 28°C, the total fecundity (eggs/female) was 71, 67, 66 and 57, respectively and the daily fecundity rate (eggs/female/day) was 5.6, 8.7, 8.7 and 9.1, respectively. The sex ratio (female/male) ranged from 1.9 to 2.1 at 16–28°C. At 16, 20, 24 and 28°C, the intrinsic rate of natural increase (r _m) was 0.11, 0.18, 0.22 and 0.27, respectively, and the population doubling time was 6.1, 3.9, 3.2 and 2.5 days, respectively. All life stages of the mite died when exposed to 35°C constant temperature for 24h, or to 32°C constant temperature for 12 days or to 31–35°C (average 32.9°C) ambient temperature for 4 days. Brennandania lambi completed development only when fed on Ag. bisporus mycelium growing on mushroom compost. It could not survive on mushroom mycelia of Auricularia auricula, Au. polytricha, Ganoderma lucidum, Hericium erinaceus, Lentinus edodes, Pleurotus ostreatus, P. sajor-caju and Tremella fuciformis.     

The effect of temperature on development and fecundityof Scymnus levaillanti

Development and fecundity of Scymnus levaillanti(Mulsant) were recorded at fiveconstant temperatures ranging from 15 to 35 ± 1 °C in 5 °C increments, 60 ± 5% RHand 16 h of artificial light (5000 Lux). Developmentaltime (egg to adult) of S. levaillantisignificantly decreased with increasing temperatures,ranging from 63.9 days at 15 °C to 11.1 days at35 °C. Development from egg to adult required305.2 DD above a developmental threshold estimated as11.7 °C. Oviposition periods lasted 86.5, 76.1,47.2, and 31.5 days at 20, 25, 30 and 35 °C,respectively. No eggs were deposited at 15 °C.Higher temperatures resulted in shorter generationtimes (T_O) and in decreased net reproductiverates (R_O) of the coccinellid. S.levaillanti kept at 30 °C produced 0.151females/female/day, the highest per capita rate ofpopulation growth (r_m). The `functional response'of larvae and adults of S. levaillanti matcheswell that described by Holling (1959) as Type 2.Daily number of eggs deposited by females increased toa plateau with increasing prey density. Resultsobtained here provide information about the biology ofS. levaillanti, and its feeding capacityindicates that it may act as an important control agent.     

The effects of temperature and host density on the development and survival of Copidosoma koehleri

Developmental rates for Copidosoma koehleri Blanchard (Hymenoptera: Encyrtidae) and its host, Phthorimaea operculella (Zeller), were determined at 10, 15, 23, 27, 29, 32, 34 and 35°C from host egg to adult. The developmental rates determined for both species showed good fit to mathematical models of insect development. At 15°C mean emergence of adult C. koehleri was 15 days after P. operculella adults emerged. At 29°C mean emergence of C. koehleri was only 5 days after that of P. operculella. P. operculella developed at 35°C, but parasitized larvae, and therefore C. koehleri, did not tolerate temperatures above 32°C. In the presence of C. koehleri, host survival was low (3%) at low host egg densities, but greater (20%) at higher host densities. Parasitized larvae of P. operculella were less able to compete for food resources, as measured by adult emergence.     

Population growth rate of the parasitic rotifer Proales gigantea,and susceptibility to parasitization in the snail Lymnaea acuminata at different stages of embryonic development

Developing eggs of the host snail Lymnaea acuminata were experimentally parasitized with the parasitic rotifer Proales gigantea to study the population growth rate of the parasite within the snail egg capsule and the susceptibility of the host eggs at different stages of embryonic development. The population growth rate of P. gigantea was 0.46 ± 0.07 individual^–1 day^–1 at the ambient temperature of 18–22 °C. Snail eggs were most susceptible to rotifer attack during the initial stages of development, becoming progressively more resistant after the hippo stage. Yet, regardless of the stage of development, the host embryo was doomed to die without hatching even if one individual rotifer gained entry inside the egg capsule. The presence of P. gigantea within the parasitized egg capsules or in the mucilage had no effect on the developmental rates and hatching success of non-parasitized eggs within the same egg mass.     

Development and reproductive biology of Laricobius nigrinus, a potential biological control agent of Adelges tsugae

Biological studies on Laricobius nigrinus Fender (Coleoptera: Derodontidae) were conducted in the laboratory to obtain basic information on this littleknown predator. Laricobius nigrinus is acandidate biological control agent of thehemlock woolly adelgid, Adelges tsugaeAnnand (Homoptera: Adelgidae), an exotic peston eastern (Tsuga canadensis (L.)Carrière) and Carolina (T.caroliniana Engelmann) hemlocks in the easternUnited States. It is univoltine andundergoes an aestival diapause. Post-aestivation activity period was 36.6 and30.8 weeks for males and females, respectively. Adult activity and oviposition are wellsynchronized with the over-wintering generationof A. tsugae. Mean lifetime fecunditywas 100.8 eggs over a mean duration of 13.2weeks oviposition period. Within thetemperature range (12–18°C) studied,development was fastest at 18°C. Meandevelopment time from egg to adult was 88.8,64.8 and 46.6 days at 12, 15 and 18°C,respectively. Laricobius nigrinus hasfour larval instars. Mean larval consumptionwas 225.9 and 252.3 A. tsugae eggs at 12and 18°C, respectively. Thesefindings provide essential data on the rate ofdevelopment and feeding capacity of L. nigrinusat temperatures typical of ambientconditions during late winter/early spring inVirginia. Its rapid development at18°C indicates that it has potential asa biological control agent of A. tsugaebecause of its synchrony with the developmentof the over-wintering generation of A. tsugaein eastern United States.     

Life Tables of Phytoseiulus Macropilis (Banks) (Gamasida: Phytoseiidae) at Different Temperatures

The biology of Phytoseiulus macropilis (Banks) fed on Tetranychus urticae Koch was studied at different temperatures. The total development times averaged 7.5, 5.7, 4.2, 4.2 and 5.6 days at 20, 25, 28, 30 and 32°C, respectively at 78 ± 2% RH and 16 h photoperiod daily. The intrinsic rate of natural increase (r _m) and the net reproduction (R _o) reached maximum values 0.47 and 88.9, respectively, at 28°C. The mean generation time decreased (20.0-8.8 days) with increasing temperature 20-28°C.     

Relationships between temperature, development and survival of different life stages of the tomato fruit fly, Neoceratitis cyanescens

The development and survival of female Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae) from egg to complete ovarian maturation were studied in the laboratory at five different constant temperatures: 15, 20, 25, 30, and 35 °C. The aim of this study was to get information on the influence of temperature on pre-mature stages, as a prerequisite to optimise rearing procedures and to understand temporal and geographical patterns of fruit fly occurrence. The developmental rate of the different life stages increased linearly with increasing temperatures up to 30 °C. The fastest development of pre-mature stages was recorded at 30 °C (22±1 days) and the slowest at 15 °C (98±3 days). The day-degrees requirements (K) to complete total development were 432.6 day-degrees. Lower temperature thresholds were 11.4, 11.9, 10.0, and 11.1 °C for egg, larval, pupal stages and ovarian maturation, respectively. The number of adults obtained from an initial batch of 100 eggs reached a maximum (64) at 25 °C. At 35 °C, no adults emerged. Larval developmental time was significantly shorter in green tomato fruits than in potato tubers at 15, 20, and 25 °C. Mortality rate of larvae was higher in green tomato fruits than in potato tubers at 25 and 30 °C.     

Field and laboratory studies on the timing of oviposition and hatching of the western black-legged tick, Ixodes pacificus (Acari: Ixodidae)

The timing of oviposition and hatching of Ixodes pacificus was investigated in the field and at constant temperatures in the laboratory. Replete females held at temperatures between 9 and 29°C began depositing eggs a mean of 9–70 days after drop off. Egg masses held between 12 and 25°C commenced hatching 25–178 days after the onset of oviposition. Eggs held at 9 or 29°C did not hatch. The lower temperature thresholds for development (LTD) for oviposition and hatching were 6.5 and 9°C, respectively. The number of degree days required for oviposition and hatching was 173 and 588, respectively. Replete females placed in the field on 2 December through to 8 March deposited eggs from 2 February through to 24 April; the eggs commenced hatching between 2 July and 21 August. Unfed larvae from two of 20 egg masses survived through the winter and fed readily when exposed to deer mice (Peromyscus maniculatus) on 22 April. Replete larvae were returned to the field and moulted between 9 and 21 August. Larvae exposed to deer mice in August, 4 weeks after hatching, also fed readily. Although further studies are needed to clarify the timing of nymphal development, the present study suggests that I. pacificus requires more than 1 year to complete its life cycle.     

Life table and biological characteristics of Macrolophus pygmaeus when feeding on Myzus persicae and Trialeurodes vaporariorum

The life table and biological characteristics of the predatory bug Macrolophus pygmaeus Rambur (Hemiptera: Miridae) were studied when the bugs were fed with Myzus persicae (Sulzer) (Homoptera: Aphididae) feeding on eggplant and with Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) feeding on tomato plants. The tests were done at five temperatures between 15 and 30 °C, using a L16:D8 photoperiod and 65 ± 5% r.h. Most eggs (range 85 to 90%) hatched at 15 and 20 °C. Incubation period was shortest at 27.5 °C (8.45 and 8.38 days on eggplant and tomato, respectively). Preoviposition was also shortest at 27.5 °C (5.10 and 4.75 days on eggplant and tomato, respectively) whereas fecundity was highest at 20 °C (213.90 and 228.25 eggs on eggplant and tomato, respectively). Maximum longevity of females was at 15 °C (122.40 and 129.35 days on eggplant and tomato, respectively). Mean generation time was longest at 15 °C on both host plants (122.75 and 124.64 days, respectively). The intrinsic rate of increase of M. pygmaeus was highest at 27.5 °C with similar values on eggplant (0.0981 day^–1) and tomato (0.1040 day^–1). Doubling time was shortest at 27.5 °C (7.06 and 6.67 days on eggplant and tomato, respectively) and, also, finite rate of increase was highest at 27.5 °C (1.1031 and 1.1096 on eggplant and tomato, respectively). The results show that the predator M. pygmaeus develops well on the aphid M. persicae or on the whitefly T. vaporariorum, both of which are important pests of vegetable crops. This predator is also well adapted to the temperatures that occur both in greenhouses and in the open field in the Mediterranean region. Compared to other natural enemies of whiteflies, such as Encarsia formosa Gahan (Hymenoptera: Aphelinidae), Macrolophus pygmaeus can increase at relatively low temperatures.     

Life-history traits of the acarophagous lady beetle,<Emphasis Type="Italic">Stethorus japonicus</Emphasis> at three constant temperatures

Stethorus japonicusKamiya (Coleoptera: Coccinellidae) is an indigenous ladybird beetle in Japan, which feeds on many spider mite species. We evaluated the development, survivorship and life-history parameters of this lady beetle on a diet of eggs of the two-spotted spider mite, Tetranychus urticae Koch (red form) (Acari: Tetranychidae). In addition, the effect of short photoperiod on its reproduction was assessed. Survival rates from egg to adult were more than 71% at temperatures between 17.5 and 30 °C. The highest immature mortality was 100% at 35 °C followed by 76% at 15 °C and 52% at 32.5 °C. The lower threshold temperature for development from egg to egg-laying adult was 13.0 °C and the thermal constant was calculated as 238.7° days. Based on these data, the maximum number of generations that could complete development in a year under field conditions in Ibaraki, central Japan, would be between five and seven. The intrinsic rates of natural increase (r_m) were 0.093 at 20 °C, 0.156 at 25 °C and 0.241 at 30 °C. Reproductive diapause was induced at photoperiods with light phases shorter than 13 h at 18 °C.     

Effect of constant temperatures on development of the walnut husk fly,Rhagoletis completa

The developmental rates of various life stages ofRhagoletis completa Cresson (Diptera: Tephritidae) were determined in the laboratory at seven different constant temperatures: 8, 12, 16, 20, 24, 28, and 32±1°C, RH 80±10%, photoperiod L 16∶D8. Preoviposition developmental rate was fastest at 28°C (10±1 days, mean±SD) and slowest at 12°C (26±1 days). About 83% of the females deposited eggs at 20 and 24°C and only 25% oviposited at 32°C. Females laid the highest number of eggs at 24°C and the lowest at 8°C. Egg development increased with increasing temperatures up to 28°C, then declined. The fastest egg development was noticed at 28°C (55±1 h) and slowest at 8°C (389±2 h). Over 90% egg hatch was observed at temperatures between 12 and 32°C, but decreased to 73% at 8°C. Larval development was fastest also at 28°C (20±0.2 days). Over 65% pupation was recorded at 20 and 24°C, but decreased to 15% at 32°C and 12% at 8°C. Pupal development was most rapid at 24°C (53±1 days) and slowest at 8°C (162±2 days). More than 70% of adult emergence was noticed in treatments between 16 and 24°C but decreased to 20% at 8°C. Based on a linear regression model of temperature-development rate relationship, the lower developmental thresholds were determined to be 6.6, 5.3, 2.9, and 5°C for preoviposition, egg, larval, and pupal stages, respectively. Based on a non-linear developmental rate model, the upper developmental thresholds were 34°C for preoviposition, egg, and larval stages and 30°C for pupal stage.     

Effects of storage at low-temperature of various heteropteran host eggs on the egg parasitoid, <Emphasis Type="Italic">Trissolcus semistriatus</Emphasis>

Various heteropteran host eggs stored under two low-temperatures were tested in the laboratory for their usability in the production of sunn pest egg parasitoid, Trissolcus semistriatus. Parasitism, adult emergence rate and development time were assesed on stored and fresh eggs of Eurygaster integriceps, Dolycoris baccarum, Graphosoma lineatum and Eurydema ornatum. Masses of fresh host eggs in microcentrifuge tubes were maintained at +6 °C and −20 °C. Every 30 days, 50 eggs of host species were exposed to parasitism by T. semistriatus. The host eggs stored at 6 °C remained viable to parasitism by T. semistriatus up to 2 months, while those of stored at −20 °C were parasitized at high rates up to 4 months, alhough succesful parasitism rates decrease with time. However, it was indicated that both fresh or stored E. ornatum eggs were not preferred to parasitism by the parasitoid. A longer development time from egg to adult was observed in stored eggs under two tested storage techniques when compared with fresh eggs.     

Encapsulation of eggs of the encyrtid wasp, Metaphycus swirskii, by the hemispherical scale, Saissetia coffeae: Effects of host age and rearing temperature

The combined effects of host age and rearing temperature upon the encapsulation of eggs of Metaphycus swirskii Annecke & Mynhardt (Hymenoptera: Encyrtidae) by the hemispherical scale, Saissetia coffeae (Walker) (Homoptera: Coccidae), were determined. Encapsulation incidence at 16, 20, 24 and 28°C increased with the age of the host, being 5.5–19.6% in 3rd instar nymphs, 45.4–74.2% in young female scales and 88.8–100% in preovipositing female scales. Within each host physiological age range, encapsulation frequency was not materially influenced by most of the temperatures. At 32°C, regardless of host age, S. coffeae encapsulated 99.5 to 100% of parasitoid eggs. Complete immunity to successful parasitism by M. swirskii occurred at 20, 24, 28 and 32°C in preovipositing female scales and at 32°C in 3rd-instar nymphs and young female scales of S. coffeae.

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Résumé Cette étude a déterminé les effets combinés de l'âge de l'hôte et de la température sur l'encapsulation des oeufs de M. swirskii Annecke & Mynhardt (Hym. Encyrtidae) par S. coffeae Walker (Homopt. Coccidae). La fréquence d'encapsulation à 16, 20, 24 et 28°C a augmenté avec l'âge de l'hôte, 5,5–19,6% dans les larves de 3ème stade, 45,4–74,2% chez les jeunes femelles et 88,8–100% chez les femelles avant la ponte. Dans chaque gamme d'âge physiologique de l'hôte, la fréquence d'encapsulation n'est pas influencée par la plupart des températures. A 32°C, quel que soit l'âge de l'hôte, S. coffeae a encapsulé 99,5–100% des oeufs du parasitoïde. Une immunité complète au parasitisme par M. swirskii a été obtenue à 20, 24, 28 et 32°C pour les femelles de cochenilles dans la période précédant la ponte, et à 32°C pour les larves de 3ème stade et les jeunes femelles de S. coffeae.

     

Temperature influence on cohort parameters and demographic characteristics of the two cowpea coreids Clavigralla tomentosicollis and C. shadabi

Age-specific life tables of two important pests of cowpea, Vigna unguiculata (L.) Walp., the pod sucking bugs Clavigralla tomentosicollis Stål and C. shadabi Dolling (Heteroptera: Coreidae), were obtained from observations carried out at different temperatures. A biophysical model was found satisfactory to describe the temperature-response of developmental and mortality rates of egg and nymphal stages, with a peak developmental rate around 34°C in both species. The variability in development times was small and the experimental data did not permit any conclusion with regard to the Erlang probability density function. Survival of eggs and nymphs remained high between 20° and 30°C for both species. At temperatures above 34°C, C. tomentosicollis survivorship and fecundity was higher than that of C. shadabi, which in turn laid more eggs at temperatures between 20° and 30°C. Maximum fecundity is estimated to be at 29°C for C. tomentosicollis (99 eggs/female) and 26°C for C. shadabi (261 eggs/female). At 30°C, the intrinsic rate of increase reached a maximum in both species, 0.152 per day for C. tomentosicollis and 0.145 per day for C. shadabi, and remained high for C. tomentosicollis until 36°C. C. tomentosicollis performed significantly better on pigeonpea, Cajanus cajan Millsp., than on cowpea at higher temperatures.     

Ovipositional Phenology and Behavior of the Spruce Cone Fly, Strobilomyia neanthracina (Diptera: Anthomyiidae)

The behavior of Strobilomyia neanthracina Michelsen, a phytophage infesting spruce (Picea spp.) seed cones, was observed at a field site in northern Ontario and in cages in a greenhouse to investigate spatiotemporal aspects of mating, host location, and oviposition. In the field, adults emerged from 21 to 24 May 1996, which coincided with bud burst of Picea glauca (Moench) Voss seed cones. For 4 days following emergence, Strobilomyia flies could no longer be seen at a monitored P. glauca tree and may have been on a mating or dispersal flight. Subsequently, females but not males were seen again and the oviposition period of ca. 3 weeks began. Mating was observed only in the greenhouse, mostly (i.e., 65%) at age 5–9 days. Although copulations lasted 11–45 min, these females laid infertile eggs only, beginning at age 4 days. No sperm was found in the spermathecal capsules of females, suggesting that no sperm had been transferred during these copulations. In both the field and the greenhouse, ovipositional sequences that resulted in egg deposition occurred throughout the day but few sequences were observed before 1000, probably because flies were not very active at air temperatures below 14°C (most sequences occurred at 25–27°C). In the greenhouse, the typical ovipositional sequence lasted an average of 7 min and consisted of landing on the cone and examining it with the proboscis and sometimes the ovipositor, egg deposition, and postovipositional behaviors such as tapping (touching the cone surface with the flabellum ca. 5 times s ^–1 ), which possibly represents a host marking behavior. In the field, tapping was seen less frequently than in the greenhouse but occurred significantly (P = 0.014) more often after sequences that resulted in egg deposition than after sequences that did not. Eggs hatched after 4–5 days at 20°C. In the greenhouse, the median longevity of females and males was 24 and 17 days, respectively.     

Life history and demography of the predatory mite,Amblyseius longispinosus Evans

The life history and demography of Amblyseius longispinosus Evans were studied under laboratory conditions 25–28°C and 65–85% RH using the red form of the twospotted spider mite, Tetranychus urticae Koch complex as prey. The entire development from egg to adult averaged 102.5 h for both sexes with a survival rate of 90.0%. Immature females consumed more prey eggs than males, averaging 7.9 and 6.4 eggs/day, respectively. The embryonic development time for male eggs was longer (average 45.2 h) than for female eggs (average 42.6 h). The average duration of succeeding stages did not differ between the sexes: larva, 15.7; protonymph, 21.1; and deutonymph, 23.0 h. Larvae were not observed to feed. Statistically significant differences between sexes were noted with respect to consumption of the deutonymphs (female, average 4.0±0.2; male, average 2.9±0.3 eggs/day) but not of the protonymphs. Mating occurred on the same day as adult emergence and was repeated several times during the reproductive life. Egg laying started on the second day after emergence. Parameters relating to oviposition were: fecundity, gross (50.7) and net (43.3) eggs/female; hatchability, 99.6% (gross) and 99.5% (net); the oviposition lasted at most 28 days and showed a peak in the first week. Net reproductive rate (R₀) was 36.7 female offspring/female/generation time (T) of 9.0 days. The sex ratio was biased toward the females (71.9%), while the intrinsic rate of increase (r_m) was 0.4 with a doubling time (DT) of 1.7 days. Males lived longer (36 days) than females (30 days) with a LT₅₀ for males of 26 days and for females of 22 days.     

The growth of Epidermophyton floccosum and E. stockdaleae at different temperatures

The ability of 17 strains of genus Epidermophyton (15 strains belonging to Epidermophyton floccosum, one to E. floccosum var. nigricans and one to E. stockdaleae) to grow at different temperatures (4 °C, 25 °C, 28 °C, 31 °C, 34 °C, 37 °C and 40 °C) was stated.The strains were inoculated on Sabouraud Dextrose Agar and regularly controled over a period of 14 days when the plates were incubated at 25 °C, 28 °C, 31 °C, 34 °C, 37 °C and 40 °C, and over a period of 70 days when the temperature was 4 °C. The optimal growth of E. floccosum was observed at 28 °C and 31 °C, and no signs of growth were recorded neither at 4 °C nor at 40 °C. The optimal development of E. stockdaleae was observed at 25 °C and 28 °C. This species grew from 4 °C to 31 °C.     

Temperature dependent development and survival of two sympatric species, Galerucella calmariensis and G. pusilla, on purple loosestrife

Two sympatric Europeanbeetles, Galerucella calmariensis (L.)and G. pusilla (Duft.) (Coleoptera:Chrysomelidae), have been released in NorthAmerica for biological control of purpleloosestrife, Lythrum salicaria L.(Lythraceae). Because establishment isaffected by environmental conditions, studieswere conducted at temperatures ranging from12.5 to 30 °C to determine differencesin rate of development and survival between thetwo species. No egg hatch occurred at12.5 °C for both species. Eggdevelopment was faster for G.calmariensis than for G. pusilla attemperatures 15 °C. Theminimum threshold temperature for eggdevelopment was lower for G. calmariensisthan G. pusilla. At 12.5 °C, G. calmariensis larvae developed 1.6 daysfaster than G. pusilla, but at 15, 20,25, and 27.5 °C G. pusilla developed2.9, 1.2, 1.1, and 0.6 days faster,respectively, than G. calmariensis. Nodifferences in developmental rate of pupa andtotal development time from egg to adulteclosion were observed for the two species. However, survival of G. calmariensisgenerally was higher than that of G.pusilla at lower temperatures. No differencewas observed in the preoviposition periodbetween the two species except at27.5 °C. The preoviposition period forboth species at 12.5 and 15 °C exceeded50 days and was much higher than for20 °C and above. The long preovipositionperiod suggests that temperatures below15 °C induce reproductive diapause. At15 °C, G. pusilla females livedlonger and also had a longer oviposition periodthan G. calmariensis. However, fasteregg and larval development, and higher survivalat 12.5 °C may give G. calmariensisa competitive advantage over G. pusillain cooler climates.     

The effect of temperature,darkness, starvation and various food types on growth,survival and reproduction of Helisoma duryi,Biomphalaria alexandrina and Bulinus truncatus (Gastropoda: Planorbidae)

Helisoma duryi has been proposed as a biological control agent in schistosomiasis due to its superiority in laboratory competition experiments with various species of the intermediate host snails. Therefore it was considered important to evaluate the response of this snail species and the intermediate host species, Biomphalaria alexandrina and Bulinus truncatus, to various physical, chemical and biological factors under laboratory conditions in order to obtain information on the similarities in the ecological niches of these species. The factors considered in the present paper are: temperature, darkness, starvation and food. All three species had optimal growth and egg laying at 26–28 °C. Only H. duryi survived for a longer period at 33°C and it was capable of starting egg laying at this temperature although the onset was delayed. However, low temperature (18°C) caused a relatively larger decrease in egg laying of H. duryi than in the other two species. Growth and egg laying was reduced for H. duryi and B. truncatus kept under darkness and B. alexandrina could not tolerate maintenance under darkness. A few days of starvation of juvenile snails had no effect on later growth and egg laying capacity of the survivors, although mortality in B. truncatus was increased. B. alexandrina had a lower tolerance to starvation than the other two species. Egg laying of snails fed only one of the three laboratory food types decreased for all three species in the order: Vov-vov (dog food in dry pellets), Tetramin (fish food) and lettuce. Combinations of lettuce and one or more proteinaceous food types gave optimal growth and egg laying for all three species.     

Reproductive bionomics of the soft tick, Ornithodoros turicata (Acari: Argasidae)

The effects of different temperatures and relative humidities (RHs) were tested on various reproductive parameters of Ornithodoros turicata, an argasid tick that inhabits gopher tortoise burrows in Florida, USA. The pre-oviposition, oviposition and incubation periods of the ticks decreased as temperature increased. These periods were also affected by the RH. The number of eggs oviposited was affected significantly by the combined effect of temperature and RH. Fewer eggs were laid by ticks in the 24°C regimes and the 27°C/95%RH regime compared to those in the other temperature/RH groups. There was an inverse relationship between the number of eggs oviposited and the percentage of hatched larvae that was correlated with the temperature and RH. Ticks reared at 27°C/90%RH and 30°C/90%RH laid more eggs than those reared in the other combinations of temperature and humidity but fewer larvae hatched from these eggs. The reproductive fitness index (RFI) values were highest in females held in the 24°C groups and the 30°C/95%RH group, although significantly more larvae hatched at the lower temperatures. The optimum reproductive conditions for O. turicata under laboratory conditions appear to be 24°C and 90–95%RH. While mating occurred at all temperatures, none of the females laid eggs at 22°C. The ticks may move preferentially to low temperatures when not feeding to remain above the critical equilibrium humidity and/or below the critical metabolic level necessary for prolonged survival. However, most female ticks oviposited after 45 days when moved to 27°C/95%RH. Ornithodoros turicata females may have a limited capability to delay oviposition until an optimal microenvironment for egg deposition can be located in the burrow.