large groups 与large numbers

有large groups的说法.它和large numbers都有“大批”的意思.如下面两个例句中它们是一种意思,可互换.
noctuid moth larvae that travel in large groups and destroy grains and alfalfa in the Plains states.
夜蛾的幼虫,成大群行动,破坏平原地区的谷类和苜蓿.
Birds gather in large numbers beside the river.
鸟儿一群群地聚在河边.
但是large numbers强调数量的时候,就不可用large groups
They supplied large numbers of tractors to the farms.
他们给这些农场提供了大量拖拉机.这里就只能用large numbers
还有large groups由字面上可看出它着重于客体形成的是团或组.如下面例句：
Our officers are moving them along and not allowing them to gather in large groups.我们的官员命令他们走开,不允许他们聚众
这里用group比较好 用number就表达不出人聚成一团的意思