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Repellent efficacies of two natural aroma compounds, citronella and citronellal, against mosquitoes, Culex pipiens pallens, were evaluated both in field and in vitro. In vitro, the experiment was conducted with three controlled bands impregnated with 30% citronella extract, 15% citronella extract and 30% citronellal extract, and with bands impregnated 30% citronella in field. Data was obtained by the means of counting numbers bitten by mosquitoes per unit time, namely human bait method. Percentage repellencies of above three controlled bands were calculated at 86%, 73%, and 78%, respectively in vitro, and 80% in field, showing high repellent effectiveness against mosquitoes. This estimation was also confirmed by t‐test compared between control group and each experimental group.

In insects, the majority of stored lipids are found in the fat body, an organ analogous to vertebrate adipose tissue and liver. In Manduca sexta , triacylglycerol (TAG) constitutes more than 90% of the fat body lipids, whereas diacylglycerol (DAG) accounts for less than 2-3%. TAG is derived mainly from dietary fat, which is transferred in the form of DAG by lipophorin from the midgut to the fat body during the feeding stage. A minor source of TAG in the fat body is the de novo lipid synthesis from carbohydrates (1). We have shown recently that the uptake of DAG from midgut to lipophorin takes place by the action of lipid transfer particle (LTP) (2).LTP is a very high density lipoprotein, first purified from the hemolymph of larval M. sexta (3) [see also refs. (4, 5) for recent reviews]. LTP has also been identified in the hemolymph of Locusta migratoria (6), Periplaneta americana (7), Musca domestica (8), and Bombyx mori (9). LTP is synthesized in the fat body and secreted into the hemolymph (10). The physiological function of LTP is still not completely understood. The protein catalyzes the transfer of DAG from adult fat body to high density lipophorin (Lp), resulting in the formation of low density lipophorin (LDLp) (11), but not the reverse reaction. LTP catalyzes the transfer of DAG from the larval midgut to Lp, but not the reverse reaction (12), and from Lp to ovarioles (13). LTP also catalyzes the transfer and/or exchange of DAG between Lp or LDLp and vitellogenin (9). The protein also facilitates the transfer of other lipids from Lp to LDLp, including hydrocarbons (7), phospholipids (9), and carotenoids (14), and it catalyzes the exchange and/or transfer of DAG between Lps and human lipoproteins (15).We have been investigating the role of LTP in DAG transfer in larval M. sexta using in vitro assays. In the midgut, LTP is required to export DAG from the midgut to Lp (12). Interestingly, LTP does not catalyze the transfer of DAG from Lp to the midgut. In this paper, we describe the extension of these studies to the larval fat body and show for the first time that LTP is required for the bidirectional transfer of DAG between Lp and fat body.

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