What does the idiom "zhu si ma ji" (spider silk and horse tracks) mean, and which animal does it refer to?

"Zhu si ma ji" is an idiom known to everyone, originating from the Qing dynasty work · Wang Jiaben's "Preface to Bieya": “Greatly opening the door of interchangeable and borrowed characters, overflowing and vast, one almost suspects that no character in the world cannot be used interchangeably, yet in reality the spider silk and horse tracks, in their original and complete form, are all present in ancient books.” So what does zhu si ma ji mean? Which animal does it refer to?

What does zhu si ma ji mean?

Zhu si ma ji, pinyin zhū sī mǎ jì, means that from a hanging spider silk one can find where the spider is, and from the mark of a zao ma (a type of insect) one can trace where it has gone. It is a metaphor for the faint traces and clues left behind by an event.

Which animal does zhu si ma ji refer to?

Many people take the words literally and think that the “ma ji” in “zhu si ma ji” refers to the hoofprint of a horse. In fact, the “ma” in “zhu si ma ji” has no connection whatsoever with the mammalian “horse” that pulls carts and shafts and flies on four hooves; rather, it refers to the “zao ma, an insect that lives in burrows beside firewood stoves.”

This small insect has the scientific name “Tettigoniidae cave cricket” (Diestrammena), commonly known as “zao ma,” and belongs to the order Orthoptera, family Rhaphidophoridae. Its name varies from place to place: in Chongqing it is called “zao ji,” in Hangzhou “zao bi ji,” and in Guangdong “zao xia.” The zao ma lives in both northern and southern China, dwelling among grass, rocks, and soil crevices in the wild when the weather is warm, and moving onto stove tops when it turns cold, feeding on leftover dishes, rice crumbs, plants, and small insects.

In the Tang dynasty work "Youyang Zazu" by Duan Chengshi, Volume 17, "Guang Dongzhi Zhi Er · Insect Chapter," it is recorded: “The zao ma is shaped like a cricket, slightly larger, with long legs, and likes to burrow beside the stove. As the saying goes, when there is a ma at the stove, it is a sign of ample food.”

“Cu zhi” means cricket, which shows that the zao ma is not large in body. “When there is a ma at the stove, it is a sign of ample food” indicates that in ancient times people were accustomed to abbreviating “zao ma” as “ma.”

The Ming dynasty physician Li Shizhen also recorded the zao ma in "Bencao Gangmu · Insects III": “The zao ma is found everywhere and dwells in burrows at the stove.” This further explains the zao ma's living habits —— it frequently moves about on top of the stove. When the zao ma crawls on the stove top, it often leaves a faint trace that is hard to notice, and this trace is the “ma ji.” Because it is as hard to identify as a fine spider silk, people equated the two and called them “zhu si ma ji,” using it as a metaphor for indistinct clues connected to the root of a matter.

Since the zao ma is a small insect, “zhu si ma ji” is also often written as “zhu si chong ji” (spider silk and insect tracks). For example, in Chapter 79 of "Yesou Puyan" by the Qing dynasty author Xia Jingqu, there is the line: “Spider silk and insect tracks, roof leaks and bat saliva, neither close nor distant, intentional yet unintentional, how wondrous it is.”