Number Of Immature Stages Research Articles

Superparasitism and fitness parameters in three native wasp parasitoids (Braconidae: Opiinae) of the Mexican fruit fly, Anastrepha ludens (Diptera: Tephritidae).

Knowledge on reproductive strategies and host use in insect parasitoids is fundamental for biological control purposes. Superparasitism and multiparasitism, oviposition in a previously parasitized host by a female of the same or different species, respectively, may impact pest management decisions. Our objective was to determine the occurrence of superparasitism and multiparasitism in three species of native larval-pupal solitary endoparasitoids that attack Anastrepha Shiner species (Diptera: Tephritidae) in the Neotropical region, and the possible effect on offspring fitness parameters. Doryctobracon crawfordi (Viereck), Utetes anastrephae (Viereck), and Opius hirtus (Fischer) occur in sympatry in Mexico, and are currently under consideration for use as biocontrol agents. Experiments were conducted under laboratory conditions with females acting alone (self-superparasitism), females in groups of the same species (conspecific superparasitism), and females in mixed groups (multiparasitism). Our results showed that self-superparasitism is an uncommon strategy in the three native species and is rare under conditions of intraspecific competition. In the case of multiparasitism, a higher number of immature stages of U. anastrephae was observed, compared to those of D. crawfordi and O. hirtus. However, it is not clear yet if this was due to some adult female trait or to the competitive ability of the larvae. We conclude that most females of the native species studied appeared to avoid superparasitism, specifically when acting alone, suggesting a high discrimination ability, which is probably a result of a close relationship and evolutionary history with Anastrepha hosts.

The African citrus triozid Trioza erytreae Del Guercio (Hemiptera: Triozidae): temporal dynamics and susceptibility to entomopathogenic fungi in East Africa

The African citrus triozid Trioza erytreae Del Guercio (Hemiptera: Triozidae) is the most destructive citrus pest. Presently, biological data on T. erytreae are insufficient for important parameters like distribution, seasonal dynamics and entomopathogens. Therefore, we determined the temporal dynamics of T. erytreae along three different altitudinal gradients in Kenya. In low altitudes, females of T. erytreae reactivated and started laying eggs between late February and early March. The mean monthly number of immature stages of T. erytreae per flush shoot peaked in February, whereas adults peaked in March. For mid-altitudes, T. erytreae mean populations peaked in February, but adults were already present in December. In high altitudes, adults appeared in June, and females began laying eggs. Trioza erytreae population densities in shaded trees positively and significantly correlated with unshaded trees. There was a significant difference between adult density and maximum temperature, average temperature, solar radiation, evaporation and dew point. Furthermore, this study evaluated the effects of 11 Metarhizium anisopliae and 4 Beauveria bassiana fungal isolates against adult T. erytreae under laboratory conditions. Metarhizium anisopliae ICIPE 18 and ICIPE 69 were the most potent isolates, causing 97.5% and 82.5% mortalities within the shortest LT50 time of 4.4 and 5.9 days, respectively. The presence of Diaphorina citri Kuwayama (Hemiptera: Liviidae) on Zanthozylum capense requires further investigation. Our findings provide relevant information for early detection, monitoring and developing biopesticides against the pest.

The Seasonal Abundance of Immature Stages of the Cabbage Worm, Pieris rapae L. on Cabbage Crop in Beni Suef Governorate, Egypt

In recent years the number of cabbage worm Pieris rapae has increased in Beni Suef Governorate, and they have threatened the vegetative growth of cabbage crop, especially in the newly reclaimed areas. That study was conducted during the 2017/18 – 2018/19 seasons respectively. Results obtained revealed that there are two distinct peaks for each eggs, larvae and pupae stages per year on cabbage plants. The immature stages covered the entire period of sampling from August 2017, till April 2018 on the cabbage plant. The first peak of egg Population was recorded on November 6 2017 and another smaller peak on mid of March 2018. The maximum larval Population (770 larvae) appeared on November 13, 2017 another smaller peak (450 larvae) on beginning April 2018. Pupal population exerted two periods of abundance On the 22 November, 2017 the highest numbers of pupae were recorded and another smaller peak on mid-April 2018. We can point out that the first and second peak of these stages in 2018/19 came about one to two weeks after the previous season 2017/18. The results also showed that there were statistically significant differences between the number of immature stages and the seasons of the year in cabbage fields. The cabbage sown in autumn season was severely attacked by this pest, followed by spring season. Autumn insect population was about 2-3 folds of winter population. Knowledge of the seasonal abundance of the immature stages is of great valuable to help in planning a control program against this target pest.

Gyne and Drone Production in Bombus Atratus (Hymenoptera: Apidae)

AbstractFor over a decade, our research group has studied the biology of the native bumblebee, Bombus atratus, to investigate the feasibility of using it to pollinate crops such as tomato, strawberry, blackberry and peppers. Traditionally, captive breeding has depended on the use of captured wild queens to initiate the colonies. The goal of the current work is to investigate conditions required to produce new queens and drones in captivity. In this study, 31 colonies were evaluated under either greenhouse or open field conditions over a 15 month period. A total of 1492 drones (D) and 737 gynes (G, i.e., virgin queens) were produced by all colonies, with 16 colonies producing both drones and gynes (D&G), 11 producing only drones (D) and 4 producing neither. Some of the D&G colonies had more than one sexual phase, but no colonies produced exclusively gynes. More drones and fewer gynes were produced per colony under greenhouse conditions with the highest number of drones produced by D&G colonies. The numbers of immature stages per cell declined in colonies as increasingly more resources were allocated to the production of gynes and the maintenance of increased nest temperature.

Life cycle of Agapetus fuscipes (Trichoptera, Glossosomatidae) in a first-order upland stream in central Germany

The number of immature stages and the seasonal patterns of development are basic life history features of a stream dwelling species and knowledge about these important components are essential for understanding its adaptations to its dynamic environment. The life cycle of Agapetus fuscipes (Trichoptera, Glossosomatidae), one of the dominant scrapers in the upper and middle reaches of the Breitenbach, a first-order upland stream in central Germany, was analysed. The pronotum length and the relationship between pronotum length, larval biomass and case length showed seven distinct larval instars, contrary to earlier findings from the Breitenbach. In addition to a few trichopteran species from other functional feeding groups, A. fuscipes is the only scraping caddis fly reported to have more than five larval instars. The moult increments of pronotum length and larval biomass were distinctly lower than in glossosomatid species with five larval instars. A. fuscipes is clearly univoltine in the Breitenbach. First-instar larvae were found from July to the beginning of December, and second-instar larvae from July to January. At the beginning of December the population consisted of the instars I to V, and development did not cease during winter. The sixth-instar larvae occurred mostly in January, and the seventh-instar larvae were never present before January. The prepupae and pupae occurred in April. The last pupae were found at the beginning of September, although most of the emergence took place in June and July. At least five different immature stages with different ecological demands were present at any time throughout the year. The ecological advantage having two additional larval instars compared to other glossosomatid species may be to compensate for the high rate of mouthpart wear that occurs while the larvae feed on the rough Bunter Sandstone substratum. A further advantage may be to spread the risk of high mortality under unfavourable environmental conditions.

Control of the oriental fruit moth, Cydia molesta (Busek) (Lepidoptera: Tortricidae), at a district level by mating disruption with synthetic female pheromone

AbstractMating disruption of Cydia molesta (Busck) was attempted by treating, with pheromone, all orchards in a small but discrete peach-growing district in New South Wales for two successive years. In the final year of the trial, two former control orchards were also treated with pheromone. The efficacy of the treatment was examined by monitoring fruit and shoot damage, male captures in pheromone traps, captures of both sexes in feeding lures, mated status of wild females and numbers of immature stages in trap bands. It was concluded that mating disruption was a viable alternative to conventional insecticides.

Two Species of Simuliidae (Diptera), Cnephia ornithophilia and Prosimulium vernale, from Maryland

The finding of Cnephia ornithophilia Davies, Peterson, & Wood and Prosimulium vernale Shewell for the first time at the Patuxent Wildlife Research Center, Laurel, Maryland, is described. Larvae of C. ornithophilia were collected Nov. 15, pupae Feb. 14, and adult flies Feb. 28. No immature or adult specimens were found between Apr. 2 and Nov. 14. The greatest number of immature stages was found in a 3- to 5-foot-wide stream several hundred feet long, 1-8 inches deep, with a stream flow between 0.49 and 3.30 feet per second. The water temperature varied from 0.5° to 4.0°C, the oxygen content was 10-13 ppm; and the p H varied from 6.9 to 7.4. Larvae of P. vernale were collected Nov. 30 through March, pupae from February through Apr. 1, and adult flies from Feb. 26 through Apr. 1. No immature or adult specimens were found between Apr. 2 and Nov. 29. The largest number of immature stages of P. vernale was found in a 6- to 16-foot-wide stream, 100 feet long, and 1.2 inches deep. The stream flow was between 0.92 and 1.36 feet per second. The water temperature was 0.5°C; p H was 6.7; and oxygen content was 7 ppm.

The Growth and Age-Distribution of a Population of Insects under Uniform Conditions

This paper deals with the growth of populations of insects such as aphids that reproduce continuously under uniform conditions. Its object is to derive the relations among the different parameters of the populations: the birth rate, the death rates at different stages, the age-distribution, and the intrinsic rate of natural increase (Lotka [1945]). Interest in these relations arose from the need to estimate the size of aphid populations by indirect means; the work presented here is supplementary to that of Hughes [1961], who was responsible for initiating the experimental investigations and who saw the possibility of estimating the rate of growth of an aphid population by means of a study of its age-distribution. Insects pass through a number of immature stages (instars) which may be readily distinguished. If the average duration of each instar is known, a count of the numbers of insects in each provides a conveniently grouped age-distribution. By studying this age-distribution at successive intervals we can estimate the way in which the population is developing and thus indirectly determine the rate of growth of the population. Although the original investigation was of an aphid population, the problem will be framed in terms sufficiently general to apply to several types of insect with similar pattern of development.

Notes on the biology of the copepod Mytilicola intestinalis Steuer.

1. The free-swimming larvae of Mytilicola intestinalis can develop in theabsence of external food. Approximate figures are given for the duration of the free-living and early parasitic stages.2. Four of the twenty-one samples of Mytilus edulis collected from various parts of Ireland were infected with Mytilicola intestinalis. All the four mussel beds found to be infected were in the neighbourhood of ports.3. 72·0% of the Mytilicola which were found inhabited the part of the recurrent intestine which is embedded in the digestive gland.4. There is a significant correlation between mussel length and number of Mytilicola per mussel.5. There is a significant decrease in the numbers of Mytilicola per mussel between November to December and May to June. It is almost certain that this represents a real decrease in the copepod population, especially in the mussels larger than 55 mm., due to a death-rate which is sufficient to more than offset the increment due to new infection during November to January. In certain chosen size groups of mussels there is also an apparent decrease as a result of mussel growth in the summer, a time when new infection is very small.6. In the 50–69 mm. mussel group the number of adult Mytilicola per mussel was lowest in September. The number of immature stages was highest in November and December and lowest from May to August. Egg-bearing copepods were found through out the year. There was an excess of males in the adult population throughout the year.The writer is very indebted to the various people who assisted in collecting mussel samples especially the Irish Sea Fisheries Association; to Miss M. Davidson, B.A., who made a bacteriological examination of a mussel sample; to Dr J. P. Harding for informing him of the specimens of Mytilicola intestinalis in the British Museum collection; and to Prof. J. Brontë Gatenby and Dr J. D. Smyth of Trinity College, Dublin (where this work was carried out), for their suggestions and advice.

Some Observations on Dictyocotyle coeliaca Nybelin, 1941 (Monogenea)

1. Heavy infestations of the coelom-dwelling trematode, Dictyocotyle coeliaca, in rays are reported.2. Of seven species of skates and rays examined, 16 of 55 specimens of R. naevtis and 81 of 78 specimens of R. naevus and 31 of 73 specimems of R. radiata were infested.3 The spindle-shaped, three-sided operculate eggs are described and possible modes of exit from the male and female hosts are discussed.4. A number of immature stages have been found and descriptions are given. Unlike the adults, the opisthaptor projects prominently beyond the posterior margin of the body, but the number and arrangement of the loculi appears to be the same.5. The systematic position of the trematode is discussed.