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Biology of Gram Blue Butterfly, Euchrysops Cnejus (fabricius) (lycaenidae: Lapidoptera) and Its Relationship with the Phenology of Host-plant (vigna Unguiculata: Fabaceae)

Sajeda Akand
Environmental Biology and Biodiversity Laboratory, Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh.

M. A. Bashar
Environmental Biology and Biodiversity Laboratory, Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh.

Humayun Reza Khan
Environmental Biology and Biodiversity Laboratory, Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh.

Abstract/ Executive Summary:

The biology of the gram blue butterfly, Euchrysops cnejus (Fabricius) (Lycaenidae:Lapidoptera) and its relationship with the phenology of host plant cowpea, Vigna unguiculata L. (Fabaceae) were studied. Eggs were reared under the laboratory conditions at 28 ± 2? and 74 ± 3% RH. The incubation period of the eggs found to be 2.33 ± 0.51 days, larval developmental period 14.65 ± 0.51 days, pre-pupal period 0.30 ± 0.04 day and pupal period 5.66 ± 0.51 days. The species took 22.94 ± 0.55 days for development from egg to adult under the laboratory condition. The length of 1^st, 2^nd, 3^rd and 4^th instar larvae was 3.66 ± 0.40, 6.16 ± 0.51, 12.16 ± 0.51 and 15.33 ± 0.40 mm, respectively. The pre-pupal length was 9.16 ± 0.61 mm and the pupal length was 9.08 ± 0.37 mm. The host-plant occurs in the field from February to July. The butterfly appeared in March. The coincidence of the gram blue butterfly to its host-plant occurred between April and early July. The oviposition behavior, incubation and immature stages were found to be profoundly related with host plant phenological phases.

Keywords: Developmental stages, Euchrysops cnejus, Relationship, Vigna unguiculata, Host-plant, Phenology

Location: Germplasm Centre (GPC) of Zoological garden, Curzon Hall, University of Dhaka.

Start Date:

End Date:

Program Area: Pest Management

Commodity: Insects

Objectives:

The present study emphasized on the relationship between the developmental stages of the gram blue butterfly, E. cnejus and the phenology of its host plant V. unguiculata.

Methodology:

The eggs of Euchrysops cnejus were collected after laying on Vigna unguiculata plant by female butterflies between 10 a.m. and 12 p.m. from the Germplasm Centre (GPC) of Zoological garden, Curzon Hall (23°43′38.6″ N, 90°24′6.85″ E), University of Dhaka. The egg-laying behaviors of the butterfly species and its host plant’s phenology as well as their relationship were observed in the GPC. The seeds of cowpea were sown from the last of January to March in the study area. Within one week seedling emerged from the soil. Flowers appeared at mid April and continued to early July. At the same time fruitification started. The harvesting period remains at the end of July. The gram blue butterfly appears from March, lay eggs on flower buds or young leaves during this period. Coincidence of gram blue butterfly to its host plant happened from April and continues to the early of July. The metamorphosis of the different developmental stages of the butterfly was observed in an ambient environment of the Environment Biology and Biodiversity Laboratory (EBBL), Department of Zoology, University of Dhaka. The butterfly and its host plant species were identified, respectively. The larvae hatched from collected eggs were reared in a rectangular plastic box (36 × 30 × 15 cm). They were given the leaves and fruits of the host plants as their foods. Larval moulting took place within the box. The larvae pupated inside the rearing box. The inactive pupae with rearing box were shifted into a bigger rectangular and iron-rod framed adult emergence cabinet (53 × 46 × 92 cm) being covered all sides with mosquito net so that the newly emerged butterfly cannot fly away. The pupae inside the plastic box were left in the emergence cabinet undisturbed until adult emergence. Larval food was supplied every alternative day. The rearing boxes containing the larvae were cleaned daily by sterilized brush, forceps, sprayer, scissor etc. for keeping the larvae free from fungal infections. Pertinent data were recorded every morning. Larval length was measured with a measuring scale. The duration of different larval instars was recorded. The data were analyzed statistically. The biology of the species was studied.

Source of Information: J. Bangladesh Acad. Sci., Vol.39, No.2, 241-248, 2015

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The immature stages of butterfly are radically different from each other. Life cycle changes in butterflies are deeply related with the phenology of host plants . Along with the growth of host plant, E. cnejus complete about 2-3 generations. High abundance of this butterfly was observed from April to June. Appropriate egg laying sites and thus larval habitats are of imminent importance for the persistence of butterfly populations. Thus, the relationship between any given butterfly species and its host plant is very specific. There was a distinct synchronization between reproductive stages of V. unguiculata and developmental stages of bE. cnejus. Larvae were found to consume flower buds and young fruits (pods) as food sources. This coincidence between two biotic factors (plant and butterfly) is essential for the completion of their life cycle successfully. The knowledge of butterfly-host plants and the relationship of plant-butterfly is a prerequisite for any butterfly conservation as well as biodiversity conservation programme.

Knowledge Management: Journal