Survival Analysis and Actuarial Parameters ofSternechus subsignatus(Coleoptera: Curculionidae) Adults

Abstract

The soybean stalk weevil, Sternechus subsignatus Boheman 1836 (Coleoptera: Curculionidae), is a very serious soybean pest in the Neotropical region. Both adults and larvae feed on soybean, causing significant yield losses. Adult survival was evaluated during three soybean growing seasons under controlled environmental conditions. A survival analysis was performed using a parametric survival fit approach in order to generate survival curves and obtain information that could help optimize integrated management strategies for this weevil pest. Sex of the weevils, crop season, fortnight in which weevils emerged, and their interaction were studied regarding their effect on adult survival. The results showed that females lived longer than males, but both genders were actually long-lived, reaching 224 and 176 d, respectively. Mean lifetime (l50) was 121.88±4.56 d for females and 89.58±2.72 d for males. Although variations were observed in adult longevities among emergence fortnights and soybean seasons, only in December and January fortnights of the 2007–2008 season and December fortnights of 2009–2010 did the statistically longest and shortest longevities occur, respectively. Survivorship data (lx) of adult females and males were fitted to the Weibull frequency distribution model. The survival curve was type I for both sexes, which indicated that mortality corresponded mostly to old individuals.

Promiscous female Euxesta eluta derive nutrients for ovarian development by expelling and consuming ejaculates

“…Susequently, longevity data for each significant categorical variable were subjected to a three‐way generalized linear model with a Poisson distribution and log link function. Means (for diet and sex) were segregated with a Sidak test at α = 0.05 (Socias et al ., ).…”

“…For the experiment 2 a survival analysis was performed for each significant variable obtained from CPHM. This test was used to find significant differences among adult survival times across different groups or subgroups using the Wilcoxon‐Gehan (D) test, which assigns a greater weight to earlier survival points (Gehan, , ; Socias et al ., ) unlike CPHM. Subsequently, mean survival time (according to diet) was separated using Sidak tests ( α = 0.05).…”

Life history and overwintering in multi‐ and univoltine species of family Tephritidae in a subtropical region of northwestern Argentina

“…Finally, in order to determine the type of survival curve, survival data were fitted by the alpha–beta parameterization of the Weibull distribution, where alpha corresponds to the mean of the normal distribution of the natural logarithm of the time variable, and beta determines how the hazard rate changes over time. If beta >1, the hazard rate increases over time; if beta = 1, the hazard rate is constant over time; and if beta <1, the hazard rate decreases over time, corresponding to the Deevey (1947) type I, II, and III survivorship curves, respectively (Pinder et al., 1978; Socías et al., 2015). For all the statistical analyses, JMP v.10.0 (SAS Institute, Cary, NC, USA) and IBM‐SPSS v.22.0 (IBM, Armonk, NY, USA) were used.…”