Recently, microneedles (or microneedle arrays) for transdermal drug delivery have received increasing attention because they can provide painless, minimal invasiveness and time-released drug delivery. However, it is very difficult to design such an eligible microneedle that meets all the requirements for mechanical strength, small insertion force, and good biocompatibility. In this paper, we investigate a biomicroneedle: caterpillar spine. It is found that this type of biomicroneedle can pierce mouse skin using a very small force (about 173 μN) without fracture and buckling failures. Such excellent properties are mainly a result of its optimal geometry evolved by Nature, the high hardness, and the reasonable high elastic modulus near the tip end. This finding may provide an inspiration for the development of improved transdermal drug delivery microneedles.