Abstract:The bug had fivenymphal instars with average nymphal period of 22.2, 25.0 and 23.
5 days onsoybean, cowpea and mash, respectively. Its duration was significantly short onsoybean compared to that recorded on other two hosts. Total life cycle wascompleted in 29.75 days on soybean, 34 days on cowpea and 33 days on mash. Among the three hosts, the bug survived for significantly longer durationon soybean.
Morphometricsof different developmental stages of the bug was also recorded. Female (2.59mm 1.13mm) wasfound to be bigger in size compared to male (2.32mm 0.79mm). Biologicalparameters of the bug were studied on soybean, cowpea and black gram under laboratory conditions (temp 23-30°Cand RH 67-90%).
Keywords: Biology, Chauliops choprai,soybean, cowpea and mash.Introduction Materials andmethodsMaintenance of the stock in the laboratory Stock culture of the bean bug was maintainedseparately on potted plants of three hosts viz., soybean (Him Soya), cowpea(C 475) and black gram (Him Mash-1) under caged conditions in Department ofEntomology throughout the course of this study. For this purpose, the copulatingadults (Plate1.)of bean bug were collected from naturally infested plants of soybean, cowpeaand black gram grown under field conditions and released on potted plants ofrespective crops maintained separately under caged conditions in the lab. Theinsects were allowed to feed and multiply on the potted plants. Dried andmatured plants were periodically replaced with young plants of the samevarieties.
Various stages of the insect required for the experimentation wereobtained from the stock culture and for their feeding fresh leaves of differenthosts were obtained from the field. Biology of C. choprai on three hostsunder lab conditions Biologyof the bug was studied on three hosts viz.,soybean (cv.
Him Soya), cowpea (cv. C 475) and mash (cv. Him Mash1) underlaboratory conditions following methodology of earlier workers (Sharma andSharma 1998) with some modifications.
During the period of experimentationdaily averages of temperature and RH were recorded with the help of ThermoHygro Clock TM-2 (Mextech TM). For the purpose of recording data onvarious biological parameters of C.choprai, experiments were conducted in complete randomized design with threehosts (soybean, cowpea and mash) taken as treatments and number of individuals(eggs, nymphs and adults of the bug) kept for recording observations were takenas replications. The observations were recorded on 100 individuals (in batches)for studying different biological parameters.
Data were recorded on thefollowing parameters of the biology of the bug: i. Incubation period ii. Duration of nymphal instars iii. Total nymphal period iv. Total life cycle v.
Morphometrics of the developmental stages vi. Pre-oviposition, oviposition and postoviposition period vii. Fecundityviii. Adult longevityi) Incubation period: To know theincubation period, freshly laid eggs of C.choprai were taken from the stock culture along with leaves and placed inPetri dishes (7.
5cm in diameter) at the rate of 25 per Petri dish. To preventthe desiccation of eggs, Petri dishes were provided with a moist filter paperat the bottom. The experiment was repeated 4 times, thus, a total of 100 eggs(25 eggs/ replication) were observed on each host. The eggs were observed dailyin order to record data and to determine incubation period and per centhatching. The period between date of oviposition and date of hatching wasconsidered to be the incubation period. ii) Duration ofnymphal instars: After hatching, first instar nymphs were shifted to specimen jars (54cm) with tender leaves of host crops.
Fresh leaves were provided as fooddaily until adult stage. In order to know the nymphal period each first instarnymphs were kept in individual jar containing fresh leaves forfurther rearing. Stalks of the leaves were wrapped with moist cotton wool tokeep the leaf turgid. Moist filter paper was kept at the bottom of the jar tomaintain humidity and the mouth of the jar was covered with muslin cloth forproper aeration. Moulting periods and dead nymphs were recorded daily in orderto determine the developmental periods and survival rates of each stage.
Differentinstars were determined on the basis of their exuvae. The duration of firstinstar nymph was taken as the time period between nymphal emergence and firstmoulting. The duration of other instars were taken as the time period betweentwo successive moults. Time gap between hatching of eggs and last nymphalmoulting was taken as the total nymphal period.
iii) Pre-oviposition, oviposition and postoviposition period: After completion ofnymphal duration, adults emerged at the same day were transferred to glass chimneys(2015cm) for the purposeof mating under laboratory conditions on all the three host crops, separately. The number of eggs laid on the plants byadults were counted daily. The pre-oviposition, oviposition and postoviposition periods were recorded separately. The period between the emergenceof adult female bug to the start of egg laying was recorded as thepre-oviposition period. The time taken from initiation of egg laying to thelast egg laid by the female was considered as the oviposition period.
Post-oviposition period was taken as the time period between the last egglaying and death of female. Number of eggs laid by each female was recorded todetermine its fecundity. Number of females dying on each day of their life wasrecorded to determine age specific morality. The effect of each host onthe oviposition of the bug was recorded. iv) Adult longevity:The data on longevity of male and female, total fecundity of the bug wererecorded.
The adult longevity wasrecorded for both the sexes separately. The number of days the adult survivedwas taken as the adult longevity.Morphometrics ofdifferent developmental stages