Insects constitute one of the major components of biodiversity in tropical ecosystems. They are particularly important in the Amazon and the Congo Basin [1] . They represent three-quarters of the animal species described on the planet with around six million species [2] , a large number of insects still remain unknown in the 21st century [3] . Their interactions with plants represent particularly important scientific and societal issues since they affect the distribution and abundance of plant and animal species, consequently, the functioning and biological diversity of ecosystems as well as human well-being [4] . They make it possible, in fact, to assess the quality of ecosystems, to predict future changes and to diagnose ecological problems [5] .

In the agronomic field, they are important because, living in association with plants, they ensure their protection through predation. Some are essentially true pollinators and spreaders of plants; others cause damage to crops and cause the decomposition of organic matter. In the health field, many species are used as antibiotics for dermatological infections; still others cause allergies [6] . They parasitize or transmit pathogenic organisms to humans, livestock and plants [7] . In genetics, insects have made it possible to demonstrate the process of cloning a gene to be expressed in viral DNA [8] . In pharmacology, many of them are increasingly studied in order to isolate natural substances of medical interest. The venoms of certain species are commonly used in indigenous pharmacopoeias [9] . In the traditional domain, insects and their productions also serve as technical materials. Beeswax is widely used. The dry nests of termites and wasps can be used to light fires, or be used in traditional remedies. In the food sector, insects are part of the eating habits of many populations around the world and contribute significantly to reducing the problems of deficiencies in proteins, lipids, vitamins and/or mineral salts [10] [11] . Insects of the Dactylopiidae family, notably scale insects (Coccus cacti), are used in the production of a natural dye called carmine, used in food coloring as well as in medicines and cosmetic products [12] [13] .

In the Republic of Congo, entomological diversity is little known, because very few studies have been devoted to insects. Some works carried out, mostly old, are those of [14] - [20] . In addition, all this work is only based on the identification of the entomofauna of a few forests and savannahs in the Congo Basin. This study is a contribution to the knowledge of the diversity of the entomofauna of the natural forest of the Scientific City.

During the present study, two orders dominated the collection: Diptera followed by Hymenoptera, Coleoptera, Orthoptera, Hemiptera and Blattoptera. The study of the pests of market gardening plants on the Congo River bank carried by [19] , identified 4 main orders: Coleoptera, Diptera, Hemiptera and Hymenoptera. The diversity and spatial distribution of the entomofauna of Ignié studied by [20] found the following main orders: Hymenoptera, Orthoptera, Coleoptera, Blattoptera and Odonata. The analysis of these results shows that Hymenoptera is a main order in the three studies but in slightly different proportions. The identified Diptera, in high proportion in the Scientific City, are also found in high proportions in the study of [19] , but present in low proportion in Ignié. These results differ from those of [3] who obtained two major orders, Coleoptera and Lepidoptera, because another very effective light trap technique was applied. Indeed, the abundance of these two major orders could also be explained by the presence of an experimental field of corn and eggplants in full flowering and or fruiting in the study environment since they are true pollinators. [33] thinks that Orthoptera are very scarce during the fruiting or flowering period. These differences can be explained by varying sampling methods and techniques, as well as floristic composition. Concerning the specific richness of the orders, the student’s test (threshold 5%) with 1 factor (p = 0.001) showed that the Diptera are richer (25 species; 26%) than the Hymenoptera (23 species; 23%). This specific richness could be mainly due to the diversity of the calliphoridae and the Formicidae, whose dominant species are respectively Calliphora sp and Polyrhachis cyaniventris. These results corroborate those of [20] . This could be explained by the fact that these two forests belong to the same geographical area.

The Formicidae family is the most abundant, followed by the Callophoridae. We note that [20] also found that the Formicidae family dominates followed by the Acrididae in the part corresponding to the natural forest. These differ from the results of [20] obtained in the primary forest. This abundance of the two families would be justified by the use of more diversified sampling methods and techniques compared to those used in other works.

These results are similar to those of [1] , who worked in a gallery forest in Gabon, and also observed the abundance of Formicidae. The 1-way Wilcoxon test (p = 0.04) applied to these results showed a significant difference between certain families. However, the Kruskal-Wallis test at the 5% threshold (p = 0.56) showed no clear difference between the specific richness of the families. Indeed, the differences observed from one entomological population to another could be explained by the fact that the aforementioned study was carried out in an area where the environmental factors are different from those of the Scientific City.

These results are similar to those of [34] who worked in the tropical zone (Guyana). This richness is marked mainly by the Coccinellidae family. [35] insinuates that Coleoptera are the richest taxon on earth and a major element of biodiversity. The 1-factor Wilcoxon test (5% threshold) showed that the Formicidae are also abundant, presenting seven (7) different species, representing the highest species richness in the field (7%).

The Shannon-Weaver diversity index is relatively high and equal to 3.73, which demonstrates significant specific richness in the Scientific City Forest [32] . Equitability is equal to 0.51, a value less than 0.7, indicating a heterogeneous specific distribution, proof of population imbalance. The study on the entomofauna of the Ignié forest carried out by [20] , found a high specific diversity (H' = 4.95) linked to a homogeneity of the population (E = 0.85) in the station corresponding to the primary forest. This could result in internal ecological factors of natural forests which induce stability and a homogeneous distribution of individuals between species [36] .

These results are different from those of the Scientific City due to the logging activities carried out by the neighboring populations, during the periods of civil wars that the Congo experienced during the period from 1990 to 2000. This massive deforestation caused profound environmental changes which have led to an imbalance in the population of entomofauna. Although there are no studies prior to the period of disturbances, nevertheless we can deduce that Calliphora sp and Polyrhachis cyaniventris were able to resist the changes while the majority of the more affected species are present but in small numbers.

The inventory of the entomofauna of the Scientific City (Ex ORSTOM) was carried out, following a methodology based on the combination of several quantitative collection techniques and made it possible to invent 1523 specimens divided into 102 species, grouped into 99 genera, 59 families and 12 orders. The most abundant order is that of Diptera, formed essentially by the family Calliphoridae. However, the Formicidae family (Hymenoptera) is the most representative and diverse. Calliphora sp. and Polyrhachis cyaniventris are the two species with the highest specific relative abundance. The entomofauna of the Scientific City is very diverse, the Shannon index is equal to 3.73. Equitability is equal to 0.51, indicating a heterogeneous specific distribution of the population which is therefore unbalanced.

The authors thank Professor BANGA MBOKO Henri, Specialist of Animal Production, Superior School of Agronomy and Forestry, University Marien NGOUABI for the correction of the article English version.