A Boy with a Flying Squirrel (Henry Pelham)

Copley executed the portrait in oil on canvas, employing a palette centered on saturated crimson, deep blue, warm yellow, and pink against dark browns. Light enters from the left, illuminating the face, hands, and squirrel while casting soft shadows. The brushwork is smooth and refined, with careful attention to textures of fabric, fur, and wood grain. The artist rendered the red drapery in deep folds behind the figure, the highly polished mahogany table, and the delicate reflections in the glass of water with particular precision. Special attention was given to the squirrel, notably in the meticulous portrayal of its eyes and gliding membrane. Copley adapted his style to appeal to English viewers by idealizing the sitter's face while maintaining precise realism for material details. Technical examination has revealed that the artist carefully adjusted proportions and modified certain elements, including the table and arms, to achieve compositional balance.

Copley completed the painting by early fall 1765 in Boston, intending it for a London audience. Aware of the risks of transatlantic shipment, he had previously lost pastels in a shipwreck that spring. For this work, he assembled a professional team to ensure safe passage; the painting crossed as part of Mr. Roger Hale's baggage. Hale delivered it to Captain R. G. Bruce in London, who took it to the studio of Sir Joshua Reynolds. Benjamin West examined it beforehand and, despite lost attribution, deduced its American origin from the American pine stretcher. A letter from Copley eventually confirmed authorship, though the work was still mislabeled as by "Mr. William Copley, of Boston, New England" at the Society of Artists exhibition in 1766. Following the exhibition, the Society elected Copley a fellow and encouraged him to come to London for training. The painting later entered the collection of the Museum of Fine Arts, Boston, where it remains. It has also been exhibited at the National Gallery of Art.

By 1765, Copley had established himself as the foremost portraitist of Boston's mercantile elite, yet he remained largely self-taught and had never left New England. He aspired to become a European-style history painter and used this work to test whether his art met English standards. The painting belongs to a broader colonial American tradition of limners, marked by what art historian Barbara Novak has described as a "primitive" concern for exactitude combined with an "archaic" desire to penetrate the mystery of British court painting. Copley was not alone in his squirrel motif: in 1765 alone he produced two other squirrel paintings, Mrs. Theodore Atkinson and Boy with a Squirrel, John Bee Holmes, and he later included a squirrel in his 1771 portrait of Daniel C. Verplanck. According to critic Henry Theodore Tuckerman, Copley was intimately acquainted with the flying squirrel's natural history and kept several pet flying squirrels. Art historian Alfred Neumeyer situated the child-with-animal convention within European practice since the seventeenth century, noting its function in depicting subjects engaged in habitual leisure activity.

The 1766 London reception proved decisive for Copley's career. Joshua Reynolds commended the work as a "very wonderfull Performance" while noting "a little Hardness in the Drawing, Coldness in the Shades, An over minuteness." Reynolds advised that Copley needed proper training before his "Manner and Taste were corrupted or fixed by working in [his] little way at Boston." Despite this qualified critique, the overall praise from Reynolds and contemporaries like Benjamin West, who exclaimed "What delicious coloring! worthy of Titian himself!" confirmed Copley's international potential. Later historians and critics have assessed the painting as a turning point in Copley's career and a marker in American art history. The work has drawn sustained scholarly attention, including observations by historian Jennifer Rogers on the subtle formal echoes between the boy's ear, the squirrel's membrane, the spacing of fingers, the water glass, and the drapery folds. Neurologist Geoffrey Schott has also examined these perceived correspondences, though their intentional status remains debated.