Nalepa Christine A
Beneficial Insects Laboratory, North Carolina Department of Agriculture and Consumer Services, Plant Industry Division, Raleigh, NC 27699-1060, USA.
J Econ Entomol. 2007 Oct;100(5):1633-6. doi: 10.1603/0022-0493(2007)100[1633:haccib]2.0.co;2.
Although the introduced lady beetle Harmonia axyridis (Pallas) (Coleoptera: Coc-cinellidae) is an important predator of aphids in a variety of crop systems during the growing season, it is often a pest in fall and winter when it enters buildings seeking overwintering sites. One of the primary recommendations for managing this annual influx is to prevent beetle entry by caulking or otherwise filling potential entry points in buildings. The goal of this study was to determine how small a gap the beetles are able to enter in choice and no-choice studies by experimentally exploiting their behavioral tendency to seek dark shelters at cool temperatures. Within the size range of adults collected in central North Carolina in 2003 (1.99-3.29 mm body height), no beetles entered a 2-mm access during no-choice experiments. Most (83%) entered a 3-mm gap; those failing to cross the 3-mm threshold were significantly larger than those that traversed it. In choice experiments, 98.2% of beetles entered shelters. As in the previous study, no beetles entered shelters with 2-mm gaps. Significantly fewer were found in shelters with 3-mm entrances than in those with 4- or 5-mm access; beetles that entered 3-mm gaps were significantly smaller than the remainder of the test population. Although no H. axyridis crossed a 2-mm threshold in either experiment, a gap of this size may nonetheless allow admission if it has flexible borders (e.g., foam weather stripping); beetles were observed attempting forced entry into too-small crevices.
虽然引入的异色瓢虫（Harmonia axyridis (Pallas)，鞘翅目：瓢虫科）在生长季节是多种作物系统中蚜虫的重要捕食者，但在秋冬季节，当它进入建筑物寻找越冬场所时，往往会成为害虫。管理这种每年大量涌入的主要建议之一是通过填缝或以其他方式填充建筑物中潜在的入口点来防止瓢虫进入。本研究的目的是通过实验利用它们在低温下寻找黑暗庇护所的行为倾向，确定在选择和无选择实验中瓢虫能够进入的最小缝隙尺寸。在2003年从北卡罗来纳州中部收集的成虫尺寸范围内（体长为1.99 - 3.29毫米），在无选择实验中没有瓢虫能够进入2毫米的通道。大多数（83%）进入了3毫米的缝隙；未能越过3毫米门槛的瓢虫明显比越过的瓢虫体型更大。在选择实验中，98.2%的瓢虫进入了庇护所。与之前的研究一样，没有瓢虫进入缝隙为2毫米的庇护所。在入口为3毫米的庇护所中发现的瓢虫明显少于入口为4毫米或5毫米的庇护所；进入3毫米缝隙的瓢虫明显小于测试群体中的其他瓢虫。虽然在任何一个实验中都没有异色瓢虫越过2毫米的门槛，但如果缝隙有灵活的边界（例如泡沫挡风雨条），这种尺寸的缝隙仍可能允许瓢虫进入；观察到瓢虫试图强行进入过小的缝隙。
