The identification of an aphid juvenile hormone, and its titre in relation to photoperiod

ABSTRACT. Whole body extractions from larval and adult apterous forms of Megoura viciae , and from adult Aphis fabae , were analysed for the known insect juvenile hormones (JHs) by a gas chromatography-mass spectrometric method. Low levels of JH III were detected in both aphid species, the first identification of a juvenile hormone from an homopteran insect. Although the mean titre in adult M. viciae is higher in long-day than in short-day reared insects (0.12±0.03 v. 0.04±0.01 ng/g), titres were variable and measurements overlapped. The results are discussed in the context of the hormonal control of aphid polymorphism and the question of identity of homopteran and hemipteran JH.     

Impacts of Argentine ants on mealybugs and their natural enemies in California's coastal vineyards

Abstract 1. The Argentine ant, Linepithema humile, tends honeydew‐excreting homopterans and can disrupt the activity of their natural enemies. This mutualism is often cited for increases in homopteran densities; however, the ant’s impact on natural enemies may be only one of several effects of ant tending that alters insect densities. To test for the variable impacts of ants, mealybug and natural enemy densities were monitored on ant‐tended and ant‐excluded vines in two California vineyard regions. 2. Ant tending increased densities of the obscure mealybug, Pseudococcus viburni, and lowered densities of its encyrtid parasitoids Pseudaphycus flavidulus and Leptomastix epona. Differences in parasitoid recovery rates suggest that P. flavidulus was better able to forage on ant‐tended vines than L. epona. 3. Densities of a coccinellid predator, Cryptolaemus montrouzieri, were higher on ant‐tended vines, where there were more mealybugs. Together with behavioural observations, the results showed that this predator can forage in patches of ant‐tended mealybugs, and that it effectively mimics mealybugs to avoid disturbance by ants. 4. Ant tending increased densities of the grape mealybug, Pseudococcus maritimus, by increasing the number of surviving first‐instar mealybugs. Parasitoids were nearly absent from the vineyard infested with P. maritimus. Therefore, ants improved either mealybug habitat or fitness. 5. There was no difference in mealybug distribution or seasonal development patterns on ant‐tended and ant‐excluded vines, indicating that ants did not move mealybugs to better feeding locations or create a spatial refuge from natural enemies. 6. Results showed that while Argentine ants were clearly associated with increased mealybug densities, it is not a simple matter of disrupting natural enemies. Instead, ant tending includes benefits independent of the effect on natural enemies. Moreover, the effects on different natural enemy species varied, as some species thrive in the presence of ants.     

Effects of food rewards offered by ant–plant Macaranga on the colony size of ants

Myrmecophytes (ant–plants) have special hollow structures (domatia) in which obligate ant partners nest. As the ants live only on the plants and feed exclusively on plant food bodies, sap-sucking homopterans in the domatia, and/or the homopterans honeydew, they are suitable for the study of colony size regulation by food. We examined factors regulating ant colony size in four myrmecophytic Macaranga species, which have strictly species-specific association with Crematogaster symbiont ants. Intra- and interspecific comparison of the plants showed that the ant biomass per unit food biomass was constant irrespective of plant developmental stage and plant species, suggesting that the ant colony size is limited by food supply. The primary food offered by the plants to the ants was different among Macaranga species. Ants in Macaranga beccariana and Macaranga bancana relied on homopterans rather than food bodies, and appeared to regulate the homopteran biomass and, as a consequence, regulate the ants own biomass. In contrast, ants in Macaranga winkleri and Macaranga trachyphylla relied primarily on food bodies rather than homopterans, and the plants appeared to manipulate the ant colony size. Per capita plant investment in ants (ant dry weight plant dry weight^–1) was different among the four Macaranga species. The homoptera-dependent M. beccariana and M. bancana harbored lower biomass of ants than the food-body dependent M. winkleri, suggesting that energy loss is involved in the homoptera-interposing symbiotic system which has one additional trophic level. The plants investment ratio to the ants generally decreased as plants grew. The evolution of the plant reward-offering system in ant–plant–homopteran symbioses is discussed with an emphasis on the role of homopterans.     

蚂蚁与排泄蜜露的同翅目昆虫的相互作用及其生态学效应

同翅目昆虫多为植食性害虫,但有些种类也是重要的经济昆虫。以蜜露为纽带,蚂蚁与排泄蜜露的同翅目昆虫在漫长的进化过程中逐渐形成了复杂而密切的关系。研究蚂蚁-同翅目昆虫之间的相互作用,有选择的防治或保护某些同翅目昆虫,并控制其在寄主植物上的数量,可提高经济效益。本文介绍蚂蚁与排泄蜜露的同翅目昆虫的相互作用,以及相互作用对节肢动物群落和寄主植物产生的生态学效益,提出研究过程中的不足,并探讨蚂蚁-同翅目昆虫之间的相互作用在生物防治、生物多样性及生态系统功能方面的重要意义,以促进种间关系研究的进一步发展。     

电子取食监测仪在植物抗虫性研究中的应用

主要综述了电子取食监测仪在植物对同翅目昆虫抗虫性研究中的应用情况.利用电子取食监测仪可监测同翅目昆虫（蚜虫、飞虱、叶蝉、蓟马、粉虱等）在不同抗、感虫品种上的取食行为,并根据取食行为参数如刺探频率、唾液分泌时间、韧皮部取食时间等在不同抗、感品种上的差异来区别品种的抗、感虫特性和确定抗虫因子存在的部位.     

植物凝集素与抗虫基因工程

植物凝集素是一类结合特异糖类的蛋白质,在农业,医学等领域要有应用前景。本文概述了植物凝集素的定义,分类,作为抗性蛋白质的证据,以及其杀虫机理,并对几个较为重要的植物凝集素及其对同翅目害虫防治方面作一阐述。