Insect Communities in the Three Different Forest Habitats of Sungai Lalang Forest Reserve with Emphasis on Selected Orders of Insects

A study to investigate the abundance and diversity of insects in forest habitat of different age after logging was conducted in the Sungai Lalang Forest Reserve, Selangor, Malaysia. The main objectives of the study were to determine (i) the dominant insect in different forest habitats, (ii) the biodiversity of insects, and (iii) the assemblage of insects that can be used as bioindicator. Three different forest habitats were selected, namely: Primary forest, Five-year-old logged forest and Ten-year-old logged forest. Various trapping methods were used to collect insects, namely: pitfall trap, yellow-pan trap, malaise trap, window trap, and sticky trap. A total of 269,547 individuals comprising of 17 orders and 361 morphospecies were collected. Four majors order represented by Diptera, Hymenoptera, Collembola and Coleoptera were recorded. The number of Diptera and Coleoptera was higher in five-year old logged forest than ten-year old logged and primary forests. The abundance of Hymenoptera was high in ten-year old logged forest, while Collembola was abundant in primary forest. These results suggest that Diptera, Hymenoptera and Coleoptera could adapt to the logged forests and they were able to utilize available resources from those forests. The richness and diversity of Hymenoptera and Coleoptera were higher in primary forest compared to both logged forests. Moreover, Collembola and Diptera had high richness and diversity index in logged forests, however the abundance, richness and diversity of insects differ among forest habitats. At the family level, Formicidae was the most dominant insect in the three forest habitats. In addition to Formicidae, Ichneumonidae, Braconidae, Phoridae, and Chrysopidae were also found in high number. The abundance of Formicidae and Ichneumonidae was higher in primary forest than in both logged forests, while Phoridae, Braconidae and Chrysopidae was higher in ten-year old logged forest than in primary and five-year old logged forests. Formicidae and Phoridae diversity and richness was higher in primary forest than both logged forests, while Braconidae and Ichneumonidae were higher in five-year old logged forest than in primary and ten-year old logged forests. Composition of Formicidae was dominated by Pheidole sp and Odontomachus sp in logged forest, while in primary forest was dominated by Camponotus sp. Microgastrinae sub-family (Braconidae) and Cryptinae sub-family (Ichneumonidae) was abundant in logged forest, while Orthocentrinae sub-family (Ichneumonidae) was numerous in primary forest. The phorid in the logged forest was abundantly represented by Megaselia, Woodiphora and Puliciphora. Of the measured habitat variables, relative humidity and litter layer were important factors affecting the abundance of Diptera, Hymenoptera, Collembola and Coleoptera in five-year old logged forest. In primary forest, litter layer was the most important factor affecting Collembola, Diptera and Hymneoptera, while canopy cover was important for Coleoptera and Collembola. Environmental factors, litter layer, relative humidity, canopy cover and understorey plant could be use as potential predictor for Diptera, Hymenoptera, Collembola and Coleoptera. Those variables, as well temperature, light intensity and rainfall, were also significant factors for Formicidae, Phoridae, Braconidae, Ichneumonidae and Chrysopidae. The composition of insects was found to be different in the three study areas. The relatively high number of insect biodiversity in the logged forest was due to the differences in habitat condition between logged and primary forest. The number of trees and understorey plants were significantly different among habitats. Apparently, after forest logging, some undisturbed forest fragment patches contribute to the higher number of species in the logged forest. This difference was also evident in species richness, abundance, composition and diversity that corresponded to the intensity level of logging, age of the logged forest, proximity of other forest habitats and the insects’ adaptability in the logged habitats. The results presented in this study show that surveys of insect should be conducted using as wide a variety of methods as possible because every method undoubtedly has at least one advantage over the other. Pitfall and yellow-pan traps had collected ground insects, such as Collembola and Coleoptera while malaise trap and window trap collected had flying insect, particularly Hymenoptera, Diptera and Coleoptera. Moreover, the high abundance of Phoridae, Formicidae, Ichneumonidaea and Braconidae, and Chysopidae in all habitats, suggested that further studies should be concentrated on this group for possible useful indicators of forest condition.

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