Cockroaches are stepping up their defenses against the poisons designed to kill them. 蟑螂对杀虫剂的防御机制正在加强。 A new study has found that German cockroaches, the most common species of the insect in the world, are developing cross-resistance to numerous insecticides. 最新研究发现，全球最常见的蟑螂种类德国小蠊正对多种杀虫剂产生交叉耐药性。 Not only were researchers in some cases unable to reduce cockroach numbers during a six-month study period, even when combining different insecticides, but they found the insects' resistance increased up to six-fold within one generation. 在某些情况下，研究人员不仅无法在为期半年的研究期间杀灭部分蟑螂，甚至使用了多种杀虫剂也是如此，而且他们发现，蟑螂的耐药性在一代之内提高到之前的6倍。 'This is a previously unrealized challenge in cockroaches,' said Purdue University professor Michael Scharf. 普渡大学教授迈克尔·沙夫说：“我们之前在蟑螂身上从未遇到过的挑战。” 'Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone.' 他说：“蟑螂同时对多种杀虫剂产生耐药性将使单纯利用化学物质控制它们变得几乎不可能。” The study published in the journal Scientific Reports focused on the species Blattella germanica L, which can be found all around the world. 这项研究发表在《科学报告》杂志上，重点研究了德国小蠊这种遍布全球的蟑螂种类。 The team tested different insecticides from different classes, and combinations of the bunch, in multi-unit buildings in Indiana and Illinois over a period of six months. 研究小组在半年时间内在印第安纳州和伊利诺伊州的多单元建筑物中测试了不同种类的杀虫剂及其组合。 Exterminators often mix insecticides of different classes to ensure they're eliminating bugs that have developed resistance to one, the authors note. 研究报告的作者指出，灭虫者通常会混合不同类别的杀虫剂，以确保能够杀灭对某一种杀虫剂产生耐药性的害虫。 Roaches were captured from the sites before the lab to assess the best treatment for each scenario. 研究人员从实验室前的多个地点捕捉蟑螂，以评估每种情况下的最佳方案。 'If you have the ability to test the roaches first and pick insecticide that has low resistance, that ups the odds,' Scharf said. 沙夫说：“如果能先测试蟑螂，然后挑选耐药性弱的杀虫剂，那就增加了杀灭几率。” 'But even then, we had trouble controlling populations.' “但是即便如此，我们也很难控制蟑螂的数量。” The team says it was able to keep the roach populations stable during the study period, but could not make a significant dent in their numbers. 研究小组称，在研究期间蟑螂数量能够维持稳定，但无法大幅减少。 With the two-insecticide mixture, the pests even appeared to thrive. 在使用了两种杀虫剂的混合物之后，蟑螂数量甚至增加了。 One of the single-insecticide experiments suggested the population was at first vulnerable to the method, and in that case they were able to mostly wipe them out. But, in another trial with 10 percent starting resistance, the population grew despite treatment. 其中一项单一杀虫剂试验表明，蟑螂起初对此很敏感，在这种情况下，大多数蟑螂基本上都被杀灭了。但是，在另一项耐药性达到10%的试验中，尽管使用了杀虫剂，蟑螂数量还是增加了。 Surviving roaches then led to more resistant offspring. 幸存下来的蟑螂会生育出耐药性更强的后代。 'We would see resistance increase four- or six-fold in just one generation,' Scharf said. 沙夫说：“我们发现，耐药性在仅仅一代之内就增加了4到6倍。” 'We didn't have a clue that something like that could happen this fast.' “我们此前不知道耐药性会发展得如此之快。” Female cockroaches can produce as many as 50 offspring during their three-month reproductive cycle. 雌性蟑螂可以在其三个月的繁殖周期内产下多达50个后代。 Even a small percentage of resistance and the potential for cross-resistance could mean a cockroach population just keeps coming back. 即便是很小的耐药性比例和交叉耐药性的可能性也意味着蟑螂会不断繁衍。 'Some of these methods are more expensive than using only insecticides, but if those insecticides aren't going to control or eliminate a population, you're just throwing money away,' Scharf said. 沙夫说：“一些杀灭蟑螂方法的成本要高于仅使用杀虫剂，但是如果这些杀虫剂不能控制或杀灭蟑螂，那就是在浪费钱。” 'Combining several methods will be the most effective way to eliminate cockroaches.' 他说：“多种方法结合将是消灭蟑螂最有效的方法。” The American cockroach (Periplaneta americana) is an omnivorous scavenger and one of the largest insect species that lives in close proximity to humans. 美国蟑螂（美洲大蠊）是一种杂食性食腐动物，是与人类生活在一起的最大的昆虫之一。 It has one of the largest genomes known to exist among insects, second only to the common locust. 这种蟑螂的基因组在已知的昆虫基因组中位于最大之列，仅次于常见的蝗虫。 In total, the species has 20,000 genes - which is the same number as a human. 美国蟑螂一共有2万个基因，这与人类的基因数量相同。 Some genes control its internal detoxification system, which means the cockroach doesn't get ill if it eats toxic food. 一些基因控制着蟑螂体内的解毒系统，这意味着如果蟑螂吃了有毒食物不会有不适反应。 More genes help it combat infections, meaning it is resilient to living in filthy conditions. 更多的基因帮助它们对抗感染，这意味着蟑螂能在肮脏的环境中生存。 Cockroaches can also regrow limbs thank to its remarkable genetic sequence. 蟑螂还能重新长出四肢，这要感谢其非凡的基因序列。 Scientists have also found that female cockroaches are so resilient they don't need a male partner. 科学家还发现，雌性蟑螂的适应力很强，不需要雄性伴侣。