The second largest and most well-known insect order Lepidoptera includes both butterflies and moths in the world. This study was started based on secondary information from present literature from different countries on the flora and fauna. So far, much study work was completed on this subject but those workers were not existing to the extension employees, policymakers, and the public in an efficient way to date. In this review paper, we can give the recent data on etymology, distribution and diversity, external morphology, different morphological parts of caterpillar, internal morphology, digestive system, circulatory system, reproduction and growth, respiratory system, and growth and role of the olfactive process in larval and adult lepidopteran insects. There are over one hundred and eighty thousand Lepidoptera species described, divided into one hundred and twenty-six families and forty-six superfamilies, and the total number of living beings was labeled as about ten percent. A result found is that the species of moths is about one hundred sixty thousand compared to one hundred seventy thousand five hundred species of butterflies in the world. Butterflies are an important category of insects that can function as sensors of environmental change. Butterflies are insects from the order Lepidoptera's macro-lepidopteran clade Rhopalocera. The study focused on the lepidopteran insects and the diversity of the world. It presents the review of research imperfect data on specific knowledge in diverse agroecological zones. This study acknowledged investigating breaches in different countries of the world. It also provides information on lepidopterans as alternative food and financial source of the world. It also helps in the sustainable agricultural field.

An experiment was undertaken to elucidate the genetic relationship between different quantitative traits for commercial cultivation and to evaluate selection criteria in pea breeding programs in five inbred parents. Their 17 F4’s derivatives in pea (Pisum sativum L.) evaluated ten characters during the winter season (November to February) of 2017-18 at the research farm, BSMRAU, Gazipur, Bangladesh. Analysis of variance explored significant differences among the genotypes for all the characters.  Phenotypic coefficients of variation (PCV) were close to genotypic coefficients of variation (GCV) for all the characters indicating less influence on the environment and potentiality of selection. A high heritability relationship with high genetic advance was observed for plant height, pod per plant, hundred seed weight, and seed yield per plot. Pod length showed a highly significant positive correlation with pod width and hundred seeds weight. Only days to first flowering showed a highly negative correlation with pod length and hundred seed weight. Path coefficient analysis revealed that plant height, pod per plant, and seeds per pod had a highly positive effect on yield per plant. Therefore, associating and selecting those traits, yield improvement must be possible in pea, and the days to maturity, plant height, pods per plant, pod length, and seed showed a considerable positive and highly significant correlation with plant height, pod per plant, seed per pod, and yield per plant at both genotypic and phenotypic levels indicating yield could be increased with the increase of days to maturity, plant height, pods per plant, pod length, and seed.

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