Contribution to the biology of the citrus bud mite, Aceria sheldoni (Ewing) (Acarina: Eriophyidae)*

In laboratory studies mites of Aceria sheldoni were reared on citrus fruit peels, beneath coloured cellophane hoods, to cater for their thigmotaxis and sensitivity to light of particular wave lengths. Hatching was most successful at 25°C and 98% r.h. but was reduced by low humidities (35–40% r.h.), when abnormal dwarf larvae emerged. The eggs hatched in 3–14 days; the length of a generation (egg to egg) was 12–33 days. The threshold of embryonic development was 9 °C and that for completion of the life cycle, egg to egg, was 12.5 °C. The average number of eggs laid per female was six (4–8). It increased to twelve (5–19) if the mite, during its larval stages, had been fed on buds. The vitality of both the eggs and the mature mites was tested by exposure to extreme low and high temperatures (below 0 °C, 39 °C): 50% of mites died after 30 min at 30 °C; 50% died after 30 min at –15 °C or lower.     

Life-history studies of Lydella jalisco (Diptera: Tachinidae), a parasitoid of Eoreuma loftini (Lepidoptera: Pyralidae)

Lydella jalisco Woodley (Diptera: Tachinidae) is a solitary endoparasitoid of the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Pyralidae), the key pest of sugarcane in Texas. This parasitoid was re-introduced into Texas in 1998 as part of a classical biological control program. Information on the biology of L. jalisco is scarce and indispensable for its propagation in captivity and understanding of L. jalisco-E. loftini interactions. Parasitoid longevity, reproductive biology and immature development were studied under laboratory conditions. At 22 °C, honey-fed mated adults lived about two weeks whereas lifespan of unmated individuals averaged three weeks. Females of L. jalisco emerged with a complement of eggs that continued to develop during the first days following emergence. Mating was necessary for embryonic development. After copulation, eggs were fertilized and gradually transferred to an elongated ovisac where they incubated for about one week before hatching. Hatching occurred in the female's reproductive tract, an attribute of true ovoviviparous reproduction. First instar larvae were available for oviposition during the female's entire lifetime. Egg load increased with adult female size; mean lifetime potential fecundity was 400 ± 140 eggs per female. Parasitoids successfully developed on second to sixth instar host larvae. However, host size at parasitization positively influenced the size of resultant adult parasitoids as well as the duration of the larval growth period which was shorter as host size increased. Parasitoid larvae did not complete development below 15 °C, whereas parasitoid larval and pupal mortality respectively reached 14 and 75 percent when temperature exceeded 30 °C. The importance of biological and reproductive attributes of L. jalisco for biological control, as well as for rearing are discussed.     

Predation of the apefly,Spalgis epius (Lepidoptera: Lycaenidae) on citrus mealybug,Planococcus citri (Hemiptera: Pseudococcidae)

The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae) is a serious pest of economically important crops worldwide. The apefly, Spalgis epius (Westwood) (Lepidoptera: Lycaenidae) is a potential predator of various species of mealybugs. Earlier investigation on its daily preying capacity and preference for prey stages on P. citri is incomplete. Hence, a study was conducted to find out the daily prey consumption ability and preference for prey stages by different larval instars of S. epius reared on P. citri in the laboratory. Through the 8-day developmental period with four larval instars, the daily prey consumption of S. epius increased from the first to the seventh day and decreased on the eighth day prior to the prepupal stage. Generally, there was a significant difference in the prey consumption on different days. When the prey stages were offered separately, the first to fourth instar larva of S. epius consumed, respectively, a mean of 199.6, 722.6, 1908.8, and 4625.6 eggs or 21.5, 77.0, 168.5, and 670.5 nymphs or 3.2, 7.2, 16.0, and 35.1 adults of P. citri. When an S. epius larva was fed on P. citri eggs, nymphs and adults separately, it consumed a mean of 7456.7 eggs, 937.6 nymphs, or 62.3 adults during its entire development. When the prey stages were offered all together, a single S. epius larva consumed 2618.4 eggs, 170.4 nymphs, and 39.7 adults of P. citri throughout its entire development. The study revealed that S. epius is a voracious predator of P. citri and thus could be utilized as a major biological control agent.     

Postembryonic development of Nymphon unguiculatum Hodgson 1915 (Pycnogonida, Nymphonidae) from the South Shetland Islands (Antarctica)

Male specimens of the sea spider species Nymphon unguiculatum, carrying eggs, larvae and postlarvae in various stages of development, were collected off the South Shetland Island at water depths between 112 and 472 m in austral summer 2006/2007. Here, we describe the external morphology of four postembryonic stages (protonymphon, instar 1, instar 2, and instar 3) carried by these specimens. We found that (1) protonymphon larvae hatch from the eggs; (2) larvae and postlarval stages have yolk reserves and are characterized by a relatively large size (average body lengths of 0.46, 0.55, 0.65 and 0.73 mm in the successive stages); (3) postlarvae remain on the ovigerous legs of males during several moults; (4) a spinning apparatus is present; (5) the development of walking legs is sequential. The larval and postlarval development of N. unguiculatum is compared with that known from other pycnogonid species.     

Larval stages of Neodiaptomus lindbergi Brehm, 1953 (Copepoda,Calanoida)

All the postembryonic developmental instars of Neodiaptomus lindbergi Brehm, 1953, reared in the laboratory from eggs, are described and illustrated. Further, the larval affinities of this species vis-a-vis certain other Indian diaptomid species are mentioned.     

The role of oxygen availability in the embryonation of Heterakis gallinarum eggs

The importance of oxygen availability in the embryonation of the infective egg stages of the gastrointestinal nematode parasite Heterakis gallinarum was studied in the laboratory. Unembryonated H. gallinarum eggs were kept under either aerobic conditions by gassing with oxygen, or anaerobic conditions by gassing with the inert gas nitrogen, under a range of constant temperatures. Oxygenated eggs embryonated at a rate influenced by temperature. Conversely, eggs treated with nitrogen showed no embryonation although when these eggs were transferred from nitrogen to oxygen gas after 60 days of treatment, embryonation occurred. This demonstrated that oxygen is an essential requirement for H. gallinarum egg development, although undeveloped eggs remain viable, even after 60 days in low oxygen conditions. The effects of climate on the biology of free-living stages studied under constant laboratory conditions cannot be applied directly to the field where climatic factors exhibit daily cycles. The effect of fluctuating temperature on development was investigated by including an additional temperature group in which H. gallinarum eggs were kept under daily temperature cycles between 12 and 22°C. Cycles caused eggs to develop significantly earlier than those in the constant mean cycle temperature, 17°C, but significantly slower than those in constant 22°C suggesting that daily temperature cycles had an accelerating effect on H. gallinarum egg embryonation but did not accelerate to the higher temperature. These results suggest that daily fluctuations in temperature influence development of the free-living stages and so development cannot be accurately predicted on the basis of constant temperature culture.     

Desiccation and egg viability of the ragwort flea beetle,Longitarsus flavicornis (Coleoptera: Chrysomelidae)

A study was conducted to investigate the effect of desiccation on the survival of eggs of Longitarsus flavicornis. Eclosion of L. flavicornis eggs in laboratory trials decreased with increasing desiccation time between 0 days (93% hatching) and 42 days (no egg hatching) at 50±2% relative humidity and 23±2°C. Probit analysis indicated that 25, 50 and 99% mortality of L. flavicornis eggs occurred after 5.7, 9.3 and 50.4 days desiccation, respectively. Egg development varied between a minimum of 8 days at 7 days desiccation to a maximum of 15 days at 28 days desiccation. Hatching span did not differ between treatments with all eggs hatching within 12 days of each other. A relative humidity of 88–100% was measured under ragwort rosettes in non-drought field conditions. This would be expected to facilitate successful egg eclosion. However, the occurrence of summer drought could be detrimental to egg survival.     

Effects of temperature on hatching rate, embryonic development and early larval survival of the edible sea urchin, Tripneustes gratilla

The temperature tolerances of embryonic and early larval development stages of Tripneustes gratilla were investigated from 13-34°C under laboratory conditions. Zygotes showed unequal cleavage at 13°C, whereas cleavage did not occurred at 34°C. Hatching was observed between 16–31°C with maximum hatching rates observed at 22–29°C. The lower and higher temperature limits for embryonic development were approximately 22°C and 29°C, respectively. Outside of this temperature range, embryos showed abnormality at different incubation times. Early larvae of this species have the ability to survive the higher temperature limit for short periods of time. Prism and 2 arm pluteus larvae survived at temperatures between 30 and 33°C, whereas 4 arm pluteus larvae survived at temperatures between 30 and 36°C for 2 h. These results suggest that the larval temperature tolerance capability of T. gratilla is stage dependent. These findings are important for understanding the life history strategy of this sea urchin in the shallow open water environment.     

Developmental morphology of the Indian cyprinid fish Barilius canarensis

Embryonic and larval development of an Indian cyprinid fish, Barilius canarensis, is described from laboratory-reared specimens. The eggs, measuring 2.1–2.4 mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk without oil globules. Hatching occurred 39–45 h after fertilization at 26.8°–27.4°C. The newly hatched larvae, measuring 4.8–5.1 mm in body length (BL) with 22 + 17 = 39 myomeres, were characterized by melanophores already deposited on the eyes. The eggs of B. canarensis resembled those of the related danionin species Candidia barbatus, Opsariichthys uncirostris uncirostris, Zacco platypus, Z. sieboldii, and Z. temminckii. Although the larvae of B. canarensis were also similar to those of the foregoing species in general morphology, they differed in having a straight notochord tip and pigmentation on the eyes at hatching and the almost entire absence of melanophores on the ventral body surface from the yolk sac to postflexion larval stages. Conversely, melanophores occurred on the anterior abdominal and pericardial cavities from the preflexion to postflexion larval stages.     

To hatch or not to hatch? Egg hatch response to larval density and to larval contact in a treehole mosquito

Abstract.

• 1 We investigated the effect on egg hatch of exposure to: (1) varying larval density, and (2) larval contact in Aedes triseriatus Say (Diptera: Culicidae). For 2 days in the laboratory we submerged eggs into a treehole water medium containing 0 (control), 4, 12 or 24 larvae that could either contact the eggs directly or were separated from them by a screen. Following treatment, abundance of microorganisms on the egg surfaces, a food source for newly hatched larvae and a proposed hatching stimulus, was assessed by counts made from serial dilutions of samples.
• 2 We discovered a complex hatching response to larval contact and to larval density, and an interaction between these two factors in their effect on microbial growth. Hatching was inhibited in the 0-larva control, even though microorganisms grew abundantly on the eggs. Hatch rate, as well as microbial counts, were high for eggs in direct contact with 4 larvae. As density increased in the larval contact treatment, microorganisms disappeared from the egg surfaces and hatch rate declined.
• 3 When protected from larval grazing, eggs supported numerous microbial colonies irrespective of larval density. In contrast to the contact treatment group, egg hatch increased with increasing larval density. These observations suggest that the combination of microbial growth and a larval factor stimulates hatch. This hatching response may have evolved because both abundant microorganisms and numerous larvae reflect a habitat of good quality.

     

Ecological studies on streptocephalus dichotomus baird

Summary Streptocephalus dichotomus occurs in a wide variety of shallow andThe maximum period during which these animals occur was 18Studies on both seasonal and day time variations of the physicoThe rate of increase in the population is more or less identical inThe length frequency distribution in the different ponds showsSex ratio does not appear to follow any definite pattern at anyFemales start to bear eggs when 1.7 cm long and the maximumTwo genera, Branchinella kugenumaensis and S. dichotomus were seenThis work formed a part of the thesis submitted for the award of the Degree of     

Life history of the spider parasitoid Zatypota percontatoria (Hymenoptera: Ichneumonidae)

The life history of polysphinctine parasitoids is poorly understood. As a result, their effect on their host has not been evaluated. Here, we present the phenology of Zatypota percontatoria, an ectoparasitoid wasp of theridiid spiders, using rich field, semi‐field and laboratory investigations of selected life‐history parameters. The wasps overwintered as larva attached to the spider abdomen and the imagos of the first generation emerged at the beginning of May. The sex ratio (F/M) of overwintered wasp larvae was 1.4. The wasp spent an average of 6.4 days in the egg stage, 27.67 days in the larval stage and 9.6 days in the pupal stage. Adult longevity was on average 14.34 days. Oviposition occurred on average 8.44 days following maturity. The wasp laid on average 0.35 eggs/day. The total fecundity was on average 7.4 eggs per wasp and decreased with age (data from unmated females). The developmental rate increased with experimental temperature up to 28 °C. The lower developmental threshold for pupae was estimated at 6.6 °C. The sum of effective temperatures for pupae was estimated at 157.8 degree days. Using daily temperature records from the Czech Republic over the last 41 years, we estimated an average of 3.5 generations of Z. percontatoria per year. Mortality was 48% in semi‐field conditions and 23% in the laboratory. The incidence of mortality was highest during egg and larval stages caused by the detachment of eggs or larvae during spider molting, the mortality of the spider‐host and egg deposition on the spider prosoma.     

Development of the cottid fish,Pseudoblennius percoides,reared in the laboratory,with brief descriptions of juvenileP. marmoratus andP. zonostigma

Embryonic, larval and juvenile development of the cottid fish,Pseudoblennius percoides were described on the basis of a series of laboratory-reared specimens. The eggs were demersal, adhesive, almost spherical in shape, measuring 1.66–1.82 mm in diameter, and with numerous various-sized oil globules. Neighboring eggs adhered to each other to form an egg mass. Hatching occurred between 13 and 16 days after spawning at a water temperature of 15.4 to I6.5°C. Newly hatched larvae measured from 6.5 to 7.3 mm, averaging 6.9 mm TL, and possessed 40 myomeres. Absorption of the yolk was completed at about 7.5 mm TL. Flexion of the notochord started and finished at about l0 mm TL and about 14 mm TL, respectively. Aggregate numbers of all fin rays were completed at over 16 mm TL, when the larvae reached the juvenile stage. The pigment pattern became the same as that of adults in juveniles longer than 25 mm TL. Lateral lines were completed at over 44 mm TL, when the juveniles attained to the young stage. The early stages of this species were clearly distinguished from those ofP. cottoides, and the juveniles of fourPseudoblennius species, i.e.P. percoides, P. cottoides, P. marmoratus andP. zonostigma, could be identified mainly by their pigment patterns.     

Protection of potato crop against Phthorimaea operculella (Zeller) infestation using frass extract of two noctuid insect pests under laboratory and storage simulation conditions

The oviposition deterrent effect of water extract of Spodoptera littoralis and Agrotis ipsilon larval frass on Phthorimaea operculella adult females was studied using two types of larval food “Natural host and Semi-artificial diet” under laboratory and storage simulation (semi-field) conditions. Extracted frass of fed larvae on semi-artificial diet showed complete oviposition deterrent effect at treatments with 4th, 5th and 6th instars of S. littoralis, also at treatments with 1st–3rd and 6th instars of A. ipsilon, while the same effect was observed when the larvae fed on castor oil leaves as a natural host only at treatment with frass extract of A. ipsilon 6th instar larvae. Presence of low amounts of phenols and flavonoids in water extract of A. ipsilon larval frass resulted in relatively more effect as oviposition deterrent to fertile adult females on treated oviposition sites, while the opposite effect was obtained in S. littoralis larval frass experiments. At semi-field experiments, the percentage reduction of laid eggs reached 100% after two?days at treatments with frass extracts of 4th and 5th S. littoralis larval instars and A. ipsilon 6th instar larvae fed on semi-artificial diet and/or castor oil leaves. Percentage reduction of laid eggs for untreated sacks reached 93.24 and 48.95% after 2 and 30?days, respectively, when placed between treated sacks, in comparison with the mean number of laid eggs for isolated control.     

Embryonic and larval traits of the temperate damselfish Chromis crusma reveal important similarities with other Pomacentridae throughout the family's thermal range

Embryonic development and larval morphology of Chromis crusma was described from five nests sampled between 21 and 25 m depth in central Chile (33°S). From each nest, a set of c. 100 randomly selected eggs were hand-collected and transported in seawater to the laboratory. Subsets of c. 30 eggs per nest were maintained in 50 ml glass containers at a constant ambient temperature of c. 12°C (range 11.5–12.9°C). Egg length (L) and width (W) and larval notochordal length (L_N) were measured from photographs. Geometric morphometric analyses were performed in newly hatched and 1 week old larvae to quantify shape changes. Ellipsoid eggs had an average (mean ± SE) size of 1.12 ± 0.05 mm L and 0.67 ± 0.02 mm W, with volume being similar throughout 15 developmental stages (i.e., ellipsoid-shaped; 0.27 mm³). Planktonic larvae hatched between 5 and 11 days at 12°C and had a mean L_N of 3.13 ± 0.25 mm, a yolk sack volume of 0.03 mm³ and an oil droplet volume of 0.005 mm³. Morphological traits at hatching included: (a) lack of paired fins and jaws; (b) single medial fin fold; (c) lack of eye pigmentation; (d) yolk sac present near anterior tip; (e) melanophores distributed along ventral surface with one pair over the forehead. In order to generate an up-to-date summary of developmental traits within Pomacentridae, we reviewed literature on egg development (e.g., shape and number of oil droplets), hatching and larval traits (e.g., morphology, pigmentation patterns). Thirty-two publications accounting for 35 species were selected, where eggs, embryonic development, hatching and larval traits were found for 26, 21, 24 and 34 species, respectively. In order to evaluate potential phylogenetic and environmental relationships within the early stages of Pomacentridae, cluster analyses (Bray Curtis similarity, group average) were also performed on egg and larval traits of 22 species divided by subfamily (Stegastinae, Chrominae, Abudefdufinae, Pomacentrinae) and thermal ranges (i.e., low: 16.5°C (range: 12–21°C), medium: 24.5°C (range:21–28°C) and high: 27°C (range: 26–28°C)), suggesting that early developmental patterns can be segregated by both temperature and phylogenetic relationships.     

Early developmental stages of greasyback shrimp,Metapenaeus ensis (de Haan, 1844) (Crustacea, Decapoda, Penaeidae)

Metapenaeus ensis was spawned and laboratory cultured untilthe post-larval stage to illustrate and describe its embryonicand larval development. Fecundities ranged between 454 000 and689 000 eggs, and {small tilde}99.2% of spawned eggs hatchedafter 12 h and 40 min at 33.5 p.p.t. and 29.0-29.1°C. Sixnaupliar, three protozoeal, three mysis and one post-larvalstages were noted. A minimum of {small tilde}10 days (249 h20 min) from the time of hatching were required to completethe larval stages by subsisting only on Chaeioceros gracilisand Tetraselmis tetrathele at varying temperature and salinityof 28.1-29.8°C and 33.5—34.5 p.p.t., respectively.The embryonic and larval developmental stages of M.ensis aregenerally similar to those of other known penaeid species, exceptfor the size and structure of diagnostic characters, setationof appendages and duration of metamorphoses.     

Development rate and lower temperature threshold in the eggs of Eurygaster integriceps (Heteroptera: Scutelleridae)

The sunn pest, Eurygaster integriceps Put. has a wide distribution in the Palearctic region. It is the most important pest problem of wheat in Turkey. The objective of this study was to attain better knowledge of the development of the sunn pest eggs. The lower temperature threshold and development rate of eggs were determined at 17, 20, 23, 26 and 32°C ± 1°C in the laboratory. A linear model was used to describe the developmental rate and temperature. The egg development required 90.9 degree‐days above the theoretical threshold of 11.7°C. The development time was 17.6 ± 0.1 days at 17°C, and 4.5 ± 0.01 days at 32°C. Incubation time was inversely related to temperature. The study showed that the eggs of E. integriceps needed shorter periods of time to complete their development than immature stages of their parasitoids Trissolcus spp.     

Effects of temperature on the development and reproduction of sugarcane top borer Scirpophaga excerptalis (Lepidoptera: Pyralidae)

To determine the effects of temperature on the development and reproduction of top borer Scirpophaga excerptalis Walker (Lepidoptera: Pyralidae), the durations of different developmental stages and reproductive capacity of S. excerptalis were measured at 20, 23, 26, 29 and 32℃. The results showed that the average durations of various developmental stages of S. excerptalis shortened with increasing temperatures from 20 to 32℃. The durations to complete one life cycle were 113.17 days at 20℃, and 39.50 days at 32℃. The developmental rate of each stage and generation was positively correlated with the temperature, which was consistent with the Logistic regression model. The temperature thresholds for egg, larval, pupal and preoviposition stages and the total cycle were 13.73, 14.73, 13.91, 13.66 and 14.10℃, respectively. The effective accumulative temperature was 112.62, 370.01, 188.17, 23.82 and 718.07 degree-days (DD), respectively. The adult longevity shortened with increasing temperatures, and the highest number of eggs laid per female was 204.74 eggs at 29℃. The survival rates of eggs, larvae and the whole generation were the highest at 26℃, which were 87.25%, 56.67% and 37.21%, respectively while the highest survival rate of the pupa was 76.69% at 29℃. There was no significant difference for the total cycle at 23-29℃. The results indicated that temperature was the key factor affecting the development and reproduction of S. excerptalis, and the optimum temperature for development and reproduction ranged from 23 to 29℃.     

Effect of temperature on the development of the immature stages ofBembidion lampros [Coleoptera: Carabidae]

The effects of temperature on survival and development of immature stages ofBembidion lampros were examined under controlled conditions in the laboratory. The duration of development was examined at 5°C, 12°C, 17°C, 19°C, 22°C, 25°C, 30°C and 32°C and found to be inversely related to temperature. Between 12°C and 30°C there was a significant difference in duration of egg development, but no significant difference in percentage of eggs hatched. The upper and lower lethal limits for egg development were estimated (c 31°C and 4°C respectively). There are 3 larval instars and one pupal stage. Development of larva plus pupa required a minimum of 20.9 days at 30°C. Between 22°C and 30°C survival from larva to the adult stage was 80%.