Population Demographics of Helopeltis bradyi Waterhouse (Hemiptera: Miridae) from Three Different Locations

Helopeltis bradyi Waterhouse has been reported to attack tea plantations in Batang District and cocoa plantations in Sleman District and Kulon Progo District. Information about the life parameters of H. bradyi reared using alternative feed cucumbers in the laboratory helps pest management efforts. This study aimed to determine the life demography of H. bradyi from two plants and three different locations. The study was conducted with cohort observations consisting of gross reproduction rate (GRR), net reproduction rate (Ro), intrinsic growth (r), average generation length (T), and population doubling time (DT) of three populations of H. bradyi . Results showed that there were differences in living individuals (ax), mortality, and life duration of the three H. bradyi populations. The survival type of the three populations of H. bradyi was classified as type IV. The survival of the three H. bradyi populations were influenced by their ability to adapt to new environments. From the three populations of H. bradyi observed, Sleman population survived longer because they had adapted to the rearing environment and were able to maintain the population numbers for two generations. Demographic parameters of H.bradyi from Sleman showed gross reproduction rate (GRR) of 88 individuals/generation, net reproduction rate (Ro) of .97 individuals/parents/generation, the increase in population rate (r) of 0.02 individuals/species/day, extended duration (T) of 39.50 days, and doubling time (DT) of 40.49 days.

There are several species of Helopeltis in Indonesia, viz.Helopeltis antonii, Helopeltis bradyi, and has been conducted by Simanjuntak et al. (2022).To provide more comprehensive information, this study will compare the biology and demography of H. bradyi from three locations and two different hosts, viz.Kulon Progo District, Sleman District, and Batang District.

Rearing H. bradyi
Helopeltis bradyi was reared in the Laboratory of Biological Control, Department of Plant Protection, Faculty of Agriculture, Universitas Gadjah Mada, with temperatures ranging between 25-28°C and humidity ranging between 61-78%.A pair of imagoes were placed in a 9 cm diameter and 16 cm tall plastic container to induce mating.Cucumbers were placed inside for feed and oviposition.H. bradyi from each location was kept in different plastic containers.Eggs on cucumber surfaces were counted every four days and cucumbers were transferred to a new container.The imagoes received new cucumber and it will be continuously replaced until dead.Helopeltis hatched from a pair of imagoes were given new cucumbers and replaced every two days.Observed parameters for each cohort were mating duration, mortality, number of eggs produced, number of eggs hatched, sex ratio, and lifespan.Observation of data started from a pair of imagoes mating until the next generation reached adults.Observations of the Sleman population were carried out on 3 pairs of insects, while the Kulon Progo and Batang populations were carried out on 2 pairs of insects.

Cohort and Demographic Analysis
Cohort observations and life tables consisted of the number of live insects at age x (ax), the probability of survival at age class x (lx), the number of individuals that died at age class x (dx), and the proportion of individuals that died to the number of individuals living at age class x (qx) (Tarumingkeng, 1994;Southwood & Henderson, 2000).To analyze insect demography, average number of individuals at age class x and the next age class (Lx=(lx+lx+1)/2), number of individuals at age class x and besides x+1 (Tx=Tx-1-Lx-1), individual life expectancy at each age class x (ex=Tx-lx), the specific personality of individuals at age class x (mx), number of off springs at age class x (lxmx), multiplication x, lx, and mx to calculate the length of generation (T), the length of generation (T= ∑ xlxmx/∑ lxmx), the gross reproduction rate (GRR=Σmx), the net reproduction rate (Ro=Σlxmx), the intrinsic rate (r=InRo/T), and when the population doubles (DT=In(2)/r) were calculated (Tarumingkeng, 1994;Kakde et al., 2014, andAli &Rizvi, 2010).

Morphological Identification of H. bradyi
Helopeltis obtained from three different locations were identified as the same species, namely Helopeltis bradyi (Figure 2).H. bradyi had smooth body surface, early-stage nymphs were yellow, 1 st and 2 nd instar nymphs were covered with setae.Body of imagoes were yellow, dark brown, brownish gray or black, and possessed transparent wings.The posterior was brighter than the anterior, and antennae consisted of four segments.These features were similar with Helopeltis morphological features from Melina et al. (2016) as H. bradyi was taken from a tea plantation, Batang.The difference between H. bradyi and other Helopeltis species is the presence of pale bands on the front, middle, and back of the femur (Figure 3).

Cohort and Life Table of Helopeltis bradyi
Observation of H. bradyi development from Sleman, Kulon Progo, and Batang were carried out successively in the fifth (F5), second (F2), and first (F1) generations.Observation of H. bradyi development from Sleman and Batang were carried out on 3 pairs of imago, while for H. bradyi from Kulon Progo was carried out on 2 pairs of imago.Observations of the three H. bradyi populations were done at 25−28°C and showed differences in life duration, survivorship, and fecundity.The highest number of eggs was produced from a pair of H. bradyi originating from cacao plants in Sleman District, followed by Kulon Progo District and Batang District, respectively 88 (Table 1), 28 (Table 2), and 14 eggs/ generation (Table 3).Research conducted by Simanjuntak et al. (2022) on H. bradyi from Kulon Progo which was also reared using cucumber at 28−30°C showed that three pairs of imago were able to produce 304 eggs.
The study of Anggarawati (2014) showed that Helopeltis sp. which was reared from 15 pairs of imagoes for 3 days on tea shoots was able to produce 30 eggs and on cocoa as many as 44 eggs.The incubation period of eggs until they hatch into 1 st instar in Sleman, Kulon Progo, and Batang populations was 6.67 ± 2.91 days, 8.50 ± 0.50 days, and 6.00 ± 3.06 days, respectively.The incubation period for  Individual numbers decreased during early instar nymph stages.The number of H. bradyi eggs from Sleman, Kulon Progo, and Batang that hatch were 62, 23, and 11 respectively.Nymphs of H. bradyi from Sleman and Kulon Progo continued until they reached adults.The number of nymphs that reached imago from Sleman population was 6 individuals consisting of 1 male and 5 females, followed by the Kulon Progo population with 2 females, and the Batang population with 1 female.The sex ratio of insects was not related to the number of eggs produced because female imagoes have been documented to be capable of producing infertile eggs (Siswanto et al., 2009).The three populations of H. bradyi also showed differences in their life duration.To complete one life cycle, the Sleman population took 34 days, while the Kulon Progo population took 34 days, and the Batang population took 23 days.
Adaptation is a form of insect survival against environmental changes (Sheikh et al., 2017).Each insect has its own criteria for environmental conditions such as temperature, light intensity, humidity, air, host, and others.The changes in abiotic factors that occur in the laboratory may affect individuals at each level of development.The rearing environment influences rearing insects (Singh, 2012).The large number of eggs produced and the number of nymphs that were able to survive to become adults in the fifth generation of H. bradyi from Sleman compared to the other two populations may be caused by the adaptation that had been formed in the new environment.The changes that occur continuously encouraged H. bradyi to adapt and be able to maintain the population size.Simanjuntak et al. (2022), stated that young Helopeltis were not able to adapt to changes in feeding sources and disturbances when the rearing area was cleaned.This is supported by Sétamou et al. (1999), which stated that the survival of the insect H. bradyi was strongly influenced by the type of host plant, even though it is classified as a polyphagous insect.The unsuitability of alternative hosts for insects will affect several aspects of their life, such as slowing their development and reducing their fecundity.This can happen because the protein and nutrient content in each type of plant is different (White, 1970;Savopoulou-Soultoni et al., 1994).H. bradyi nutritional and protein needs were not fulfilled by cucumber as alternative hosts could experience several disturbances.The low number of surviving H. bradyi from Kulon Progo and Batang indicated that these populations required several generations to adapt to their new environment.
The high mortality of H. bradyi at a young age was classified into type IV based on the survival ISSN 1410-1637 (print), ISSN 2548-4788 (online) curve or survival type.If the mortality rate at a young age was low, then it would be classified as type I.If the mortality rate was constant over time, then it would be classified as type II.If mortality was constant then it would be classified as type III (Southwood & Henderson, 2000).Observation of mortality at each stage of insect development is used to obtain demographic data.Cohort analysis included observing the proportion of living individuals (lx) which was carried out by calculating the number of individuals who survived at the previous stage, the proportion of deaths (qx) which was calculated by the number of individuals who died (dx), and the number of individuals who lived (Table 4 and Table 5).

Demographic Analysis of H. bradyi from Sleman
The number of individuals from the Sleman population that survived was the highest and still Natality, mortality, and developmental time were three aspects that determine the capacity of a population to increase or are referred to as the intrinsic growth rate (Hidayat et al., 2017).Birch (1948) states that the value of the intrinsic growth rate (r) and the decrease in environmental resources can be caused by an increase in gross reproduction value (GRR) and net reproduction value (Ro).The r value indicates the suitability of an insect species for its host, therefore the higher the r value for a host plant, the potential population of insect species to be suitable on hosts increase (Maharani et al., 2016).
Abiotic factors have an important role in the development and reproduction of insects (Gillot, 2005;Syarkawi et al., 2015).The environmental temperature will affect insect metabolism which will impact its ability to survive, while climate will affect insect abundance (Rockstein, 1973;Syarkawi et al., 2015).This was explained by Sari et al. (2022) that the low intrinsic growth rate and limited growth rate are in line with a decrease in ambient temperature.A low intrinsic rate indicates that a species has little possibility of continuing to grow (Hidayat et al., 2019).

CONCLUSION
The differences in mortality, fecundity, and survivorship among the three populations were caused by each population ability to adapt to new locations and different host plants.Cohort observations of each H. bradyi population started at different generations, but only H. bradyi of the Sleman population survived and lasted to two generations for demographic analysis.

Table 3 .
Life development of Helopeltis bradyi from Batang

Table 1 .
Life development of Helopeltis bradyi from Sleman

Table 5 .
Cohort data of Helopeltis bradyi from Batang