Initiation Of Oviposition Research Articles

Cereal Leaf Beetle: 1 Feeding and Oviposition on Winter Wheat and Spring Oats 2

The relationship of cereal leaf beetle, Oulema melanopus (L.), feeding and oviposition on wheat and oats was evaluated by using daily efficiency values, calculated by dividing the number of eggs deposited by the amount of food consumed per female. Field beetles had a greater efficiency on oats than wheat. Previous laboratory studies on ‘Lakeland’ barley seedlings found that beetles were most efficient shortly after the initiation of oviposition; but beetle feeding on oats began almost one month later than on wheat. When beetles were transferred from wheat to oats and back to wheat, a substantial increase in efficiency occurred while the beetles were on oats.

Pecan Weevil Adult Emergence, Onset of Oviposition and Larval Emergence from the Nut as Affected by the Phenology of the Pecan12

Emergence of adult Curculio caryae (Horn) from the soil apparently is unaffected by pecan variety. Hardness of the pecan shell and the gelatinous condition of the ovule appear to have an effect on initiation of oviposition. Larval emergence from infested pecans also varied consistent with the onset of oviposition and the phenology of the pecan. These findings indicate that a pecan weevil pest management program can be developed to concentrate on preventing oviposition as a management strategy.

Ovipositional Response Elicited by Normal, Irradiated, F1 Male Progeny, or Castrated Male Trichoplusia ni (Lepidoptera: Noctuidae)1

The ovipositional response of untreated Trichoplusia ni (Hubner) females that had mated to unirradiated, irradiated, F/sub 1/ male progeny from irradiated males, or castrated males was studied. Females that mated with irradiated males or F/sub 1/ sons of irradiated males oviposited fewer eggs than females that mated with control males, when all females had received a normal quantity of eupyrene and apyrene sperm. Irradiated males and F/sub 1/ sons of irradiated males that transferred an apparently normal sperm complement elicited significantly better oviposition from untreated females than did treated males that transferred mostly apyrene sperm, apyrene sperm only, or no sperm. Males in the latter categories elicited a better ovipositional response from the untreated females than was observed in virgin females. Normal eupyrene sperm and possibly at least 1 accessory fiuid are required to initiate a completely normal ovipositional response in cabbage looper females. The accessory secretion triggers a significant increase in oviposition, but the greatest increase occurs when males contribute normal amounts of eupyrene sperm. The initiation of oviposition and female receptivity may be closely related in this species. (auth)

Importance of timing, spore concentrations, and levels of spore carrier in applications of Nosema locustae (Microsporida: Nosematidae) for control of grasshoppers

In a study of microbial control of grasshoppers, Nosema locustae was applied to 10-acre plots in 2 replications of 24 treatment combinations in which the factors were (1) times of applications: 4 applications spaced over 22 days; (2) concentrations of spores: 1, 30, and 900 spores/in 2; and (3) levels of the spore carrier: 1 and 4 lb wheat bran/acre. The concentrations of spores had the most effect in reducing the densities of grasshoppers and the incidence of infection among the survivors at the last sampling (coincided with the initiation of oviposition), the average reduction in density attributed to application of 1 spore/in 2 was 21%, that attributed to 30 spores/in 2 was 46%, and that attributed to 900 spores/in 2 was 73%. The first and second applications caused the greatest reductions in density; the second, third, and fourth applications produced the highest incidence of infections. Also, a higher incidence of infection was observed among grasshoppers from plots treated with 30 spores/in 2 on 1 lb bran/acre than from plots treated with 30 spores/in 2 on 4 lb of bran/acre. Therefore, a ratio of about 0.63–0.94 billion spores/lb bran applied at a rate of 1–1.5 lb/acre (= 100–150 spores/in 2) at the time when the principal early summer species are third-instar nymphs would have resulted in overall reductions in density of 50–60%, with 35–50% of the survivors sufficiently infected so that fecundity would probably be affected. The reductions and incidence of infections would be higher in species that readily accept and use wheat bran, among which are some of the more economically important species of grasshoppers.

A method for estimating natural survival rate and mean fecundity of an adult insect population by dissecting the female reproductive organs

SummarySeveral problems were discussed in relation toMacDonald's method (MacDonald, 1957) for estimating the survival rate of a natural population of adults with varying survival rates and unstable age structure. Random samplings with a fixed sampling ratio and an appropriate census interval is pre‐requisite during the occurrence of the adults. At each sampling, female adults are dissected to know the ratio, pi, of nulliparous females in ith sample (i=0, 1, 2, 3, …,). The Σnipi/Σni gives an estimate of the ratio, Fα/F, of nulliparous females in the population where ni refers to the population size on ith census date. If a constant daily survival rate is assumed, the daily survival rate is estimated from equation (4′). When the survival rate is not constant over the period of adult occurrence, e. g. before and after the initiation of oviposition, the survival rate during pre‐ovipositional period is estimated by equation (4″). Decision of an economic census interval to obtain a reliable estimate of the ratio, Fα/F, is depending on the form of emergence curve, particularly on its duration and the length of pre‐ovipositional period. If the normal distribution can be assumed for the emergence curve, an interval less than one third of the emergence period is recommended. Concerning with insects having a long pre‐ovipositional period, a census interval which exceeds one third of the emergence period still gives a good estimate of Fα/F. The mean realized fecundity of some kind of insects can be estimated by equation (5′ or 5″) using the estimates obtained by the present method.

Histophysiology of the pituitary gland in correlation with the ovarian cycle in Tor (Barbus) tor (Ham.).

The histophysiology of the pituitary gland has been studied in correlation with the phases of the ovarian cycle in Tor (Barbus) tor. The cyanophilic cells in the proximal pars distalis display changes related to stages in the maturation of the ovary. The cyanophils, which display hypertrophy and hyperplasia and undergo degranulation and vacuolation during maturation, prespawning, and spawning periods, are identified as gonadotrops. Apparently their glycoproteinaceous contents, gonadotropin(s), control the processes of vitellogenesis, ovarian maturation, and initiation of oviposition. Depletion of glycoproteinaceous contents in these cyanophils leads to atresia of oocytes at advanced stages, but it does not appear to interfere with oogonial proliferation. The neurosecretory materials are implicated in female reproduction.

Some observations of the reproduction of the eye gnat, Hippelates pusio.

Observations of the reproductive behavior of eye gnats (Hippelates Pusio Loew) indicated that both sexes require 36 hr for sexual maturation of the imago before insemination occurs. During this period the gonads undergo considerable change. Marked transformation of the sperm cells occurs in the testes and development of the primary follicle of the ovary is initiated. Sexually mature males inseminated as many as four sexually mature females in a 24 hr period. Insemination did not appear to affect the rate of development of female ovaries. However, unmated females required a longer period for initiation of oviposition than mated females. Females laid an average of 26 eggs in an 18-day period. This number is a little more than half the number of ovarioles present in the ovaries.