http://www.lifesciencesite.com ) 2 2013;10( Life Science Journal 1207 A Study on the Sensory Structure, in Relation to Some Behavioral Ecology of the Oriental Hornet ( Vespa orientalis L.) (Hymenoptera: Vespidae) Mohamed M. Khodairy 1 and Azza A. Awad² 1 Plant Protection Department, Faculty of Agriculture, Assiut University, Assiut, Egypt 2 Zoology & Entomology Department, Faculty of Science, Assiut University, Assiut, Egypt awadazza@yahoo.com. Abstract: In the apiary of Assiut University, the oriental hornets, Vespa orientalis L., were trapped and collecting every three days by using modified wooden traps to know their fluctuation and population during their active season. Also, detect the differences on the morphology, ultra-structure, and behavior between the different casts (queen, daughter worker and male) of V. orientalis. In the present study, the fluctuation showed that hornet population began with a slight increase number during September which comprised about (12.3%). In October, a big jump occurred (52.5 %) in their number. By the first week of November, the number started to decrease (26.7%) and then disappeared at the second fortnight of November. Antenna plays an important and vital role during host finding and acceptance behavior in insect life. Like many insects, oriental hornet Vespa orientalis L., use antennal chemo- receptors to detect the hosts during its active seasons. Scanning electron microscope (SEM) studies showed five types of sensilla (Chaetica, trichoidea, basiconica, placodea and coeloconica) were distributed on the antenna of the three different casts of the hornet. These function of sensillae possibly as chemo-, and tactile receptors, responding to movements of the antennae. [Mohamed M. Khodairy and Azza A. Awad. A Study on the Sensory Structure, in Relation to Some Behavioral Ecology of the Oriental Hornet (Vespa orientalis L.) (Hymenoptera: Vespidae). Life Sci J 2013;10(2):1207- 1216] (ISSN:1097-8135). http://www.lifesciencesite.com. 167 Key words: Oriental hornet, Vespa orientalis L., population fluctuation, morphology, sensilla, sensory structure, behavior. 1. Introduction Wasps may be divided into the social wasps and the solitary wasps. Social wasps include the hornets, the yellow jackets and the large, mahogany- colored wasps known as the paper wasps. They live in communities consisting of males, females and sterile workers. The solitary wasps, including the mud daubers, potter wasps and digger wasps, produce no workers and build individual nests. Adult wasps are largely carnivorous, or meat eaters and some also eat vegetable matter, such as overripe fruit. As a rule, young wasps are fed entirely on other insects or insect remains. Several species have economic importance, because they are among the pollinators of commercial crops, and some of them feed on such destructive caterpillars as the corn-ear worm and army worm. A species that is native to Africa is known to prey on the eggs of the rhinoceros beetle, an insect that causes immense damage in coconut-growing regions. Many parasitic varieties, which lay their eggs in the body or egg of the host, are useful in the control of some harmful pests such as aphids, codling moths, and bollworms. On the other hand, Oriental hornet, Vespa orientalis L. cause many damage on the hives of useful bees in the Assiut’s region. It is considered recently the major pest and more dangerous for Egyptian beekeeping in Upper Egypt. Furthermore, it attacks and causes serious damages in many fruits orchards especially grapes, and dates before and after harvesting [1, 2]. The hornets are hovered near bee hives, attack and captures bee guard at hives entrances. Then they also catch forages from flowers [3, 4]. Sometimes, the hornets enter bee hives and carry off both larvae and pupae and fly back to their nests to feed their colony. Then, they cause weakness to the hives, and minimizing bee’s productivity. The activity of hornets is low in winter, spring and summer. While it increases to reach maximum population in the autumn, particularly during October. It starts to fall down during November, and disappears in December [5- 7]. The aim of this paper is to throw a light to study the following aspects which play an important role in controlling the most dangerous pest for Egyptian beekeeping in Upper Egypt. Also, to highlight further researches and methods related to biological and chemical controls: 1- Determine the fluctuation of the oriental hornet population in Assiut region during active season. 2- Enhance the importance of those potential chemoreceptor organs, represented on the antenna of the three different casts (queen, worker and male) and try to relate their presence with the invasive behavior of this oriental hornet.