Photo: Alan Manson / Wikimedia Commons · CC BY 4.0. Cropped; top-left source credit added.

A newly hatched Picasso bug is whitish, with red eyes. Within about 30 to 60 minutes, its body passes through pink and becomes black. Pierre Mbondji Mbondji and Dominique Pluot-Sigwalt described that change in their observations from Cameroon, published in 2000.

At roughly 1.4 millimeters long, the hatchlings stay clustered near their empty eggshells. During the first juvenile stage, they may wander and then regroup. Clustering declines in the second stage and isn’t a feature of the last three. Later nymphs develop bands, spots and wing buds as they grow through five instars, or stages between molts. They become adults without passing through a pupa.

The adult Sphaerocoris annulus can look beetle-like, but it belongs to Scutelleridae, the shield-backed bug family. Adults can reach about 15 millimeters (0.6 inches) in length. Its enlarged scutellum extends over the wings and abdomen. This is a different structure from a scarab beetle’s paired wing covers. The pronotum, a separate plate just behind the head, carries part of the Picasso bug’s pattern too.

Eleven dark-outlined areas, described in a five-four-two arrangement, help give the adult its recognizable appearance. Entomological accounts interpret the conspicuous design as warning coloration. It’s a very different look from the twig-mimicking buff-tip moth, which resembles a snapped branch when resting.

The Cameroon researchers also described color changes during adult life. Green males became more yellowish as they reached reproductive maturity; females yellowed later in life too. After examining the insects, the authors attributed those green and yellow background colors to hemolymph, the insect’s circulating body fluid, visible through the outer covering.

Growing up in bitterleaf flower heads

The Cameroon study combined observations at a coffee research station near Foumbot with laboratory work at Nkolbisson. Coffee plants grew alongside bitterleaf (Gymnanthemum amygdalinum, called Vernonia amygdalina in the paper), a shrub cultivated for its edible leaves.

Females laid egg clusters underneath bitterleaf leaves. The young shifted into flower heads, probing the flower ovaries with their piercing mouthparts. They remained in the flower heads until their molt into adulthood.

The researchers tried raising newly hatched bugs with flower clusters from coffee and several other plants growing in or near the coffee plots. None of those alternatives supported development beyond the second nymphal stage. Earlier observations cited in the paper recorded young on other daisy-family plants, so the Cameroon result describes a particular breeding relationship rather than a single host for the species everywhere.

Reared at 25°C (77°F), the insects took 56 days on average to develop from eggs into adults. The egg stage accounted for 8.5 of those days. Around Foumbot, adults fed intensively for six to eight months, including much of the wet season. Breeding started near the onset of the dry season in November, with one annual generation recorded.

Adults used both coffee and bitterleaf as food plants. The observers watched them feed on tender shoots or along leaf veins, with bouts lasting about 10 minutes. Three or four feeding bouts usually took place in the morning. The researchers reported no necrosis or lesions at the observed feeding sites.

For these bugs, coffee leaves and bitterleaf flower heads served different life stages. An adult’s meal and a nymph’s nursery could be growing side by side.