Is it true, dear Sue — Hister

The hint is hist in the last line. Hister is a mimic-beetle, named from its ability to fake death, which was Emily's wish, a quiet sister-in-law. Emily wished to keep away from a hister beetle by a thread and pin, or a cup to isolate it. With the same pin and cup she wanted to shut the mouth of Susan Dickinson.

Is it true, dear Sue? 1
Are there two?
I shouldn't like to come
For fear of joggling Him!
If I could shut him up 5
In a Coffee Cup,
Or tie him to a pin
Till I got in－
Or make him fast 9
To "Toby's" fist－
Hist! Whist! I'd come!
(F.189/J.218)
[1] Sue:: Susan Dickinson, Emily's sister-in-law.
[2] Are there two?:: This poem has only one hister beetle; the other refers to Sue.
[4] joggling:: a hint on something small. Him:: a hister beetle, hinted in line eleven.
[5, 6] shut, Cup:: to isolate the beetle with a cup.
[7] tie, pin:: to thread the beetle to a pin.
[9] fast:: fixed firmly.
[10] Toby:: a toy puppet, the puppet dog called Toby in Punch and Judy puppet show. She didn't want to hurt the beetle with a cat or dog.
[11] Hist:: a hint on hister; hist and whist demand silence.

. . . the Histeridae have the power of contracting their limbs and counterfeiting death, whence their names of Mimic Beetles, and Hister, the latter evidently derived from the Latin word Histrio, a stage mimic. ─ An Introduction to the Modern Classification of Insects (1839)

The modern puppet show of "Punch and Judy" embodies a domestic tragedy followed by a supernatural retribution, . . . and his dog Toby, are important characters in the performance. ─ The New American Cyclopaedia (1861)