Gratiana pallidula are beautiful pale green beetles around 5mm long with the broad pronotum and elytral margins typical of Cassidini. They are bivoltine in my area and overwinter as adults. These beetles are extremely easy to raise and their fast development makes them good candidates for demonstrating complete metamorphosis to school children.
In this article, I will briefly discuss 1) Finding the beetles, 2) Housing and Care, 3) Life Cycle, and 4) Observations and Articles. Also included are a few links to related videos from my Flickr albums.
I would like to express gratitude to Tyler Hedlund who first identified this beetle for me and who inspired me!
Finding Gratiana pallidula
It was not too difficult to find Gratiana pallidula in my area because, fortunately, there is an abundance of Solanum (Solanaceae) growing among wildflowers in parks. In my area, Solanum elaeagnifolium and Solanum dimidiatum are the commonly found species, and the beetles seem to prefer S. elaeagnifolium. Early in the season, it's fairly easy to find both adults and eggs on the leaves of Solanum elaeagnifolium. Often I spot munchie holes first, and then with careful examination of the plants I generally find adults who may be hiding inside curled leaves or on stems.
Solanum dimidiatum, with broad leaves, light purple blossoms, and large yellow fruit:
Solanum elaeagnifolium, with narrow leaves, light purple blossoms, and smaller yellow fruit: (note the munchie holes in the middle image)
Housing and Care
I recommend using large butterfly cages for raising these beetles. I use a large mesh cage measuring 36"x24"x24" that can accommodate some potted plants in 4-inch or pint-sized pots.
Both larvae and adults of this beetle feed on Solanum species. Our native Solanum species are difficult to transplant, so I used Solanum melongena (common eggplant), which is easy to grow from seed and generally easy to find in nurseries (be sure to buy only organic!). The beetles adapt well to Solanum melongena and develop from egg to adult just fine on this plant.
Care for these guys is quite easy. Just keep a fresh supply of plants that are watered (fairly deeply every other day worked for me). When I raised Deloyala guttata, another tortoise beetle who used morning glory, I found that they sometimes tried to fly out of the cage: they are quite agile flyers. However, Gratiana pallidula are much less likely to fly and are content to rest on leaves and crawl around. This relative passivity adds ease to raising these beautiful creatures.
Life Cycle
EGG:
It took me a while to figure out that the strange and intricately fashioned structures I was seeing on Solanum leaves were oothecae of Gratiana pallidula. They appear on the tops of leaves as stacked layers of a semi-transparent membrane containing light tan eggs. Sonia Casari and Édson Possidônio Teixeira (2010) describe the oothecae of a similar species, Gratiana conformis, as this: "The egg cases are formed by layers of yellowish-brown translucent membrane ... One or two eggs are laid between two membranes, starting on first or second membrane, and each egg case has from 3-8 layers of membrane." Of specifically Gratiana pallidula, the authors state, "In G. pallidula, the egg cases were fixed on the upper surface of the foliage, especially on the leaves near terminal, stacked vertically in one or two tiers."
(1)
adults with ootheca:
LARVA:
The larvae are a pale green with pale "fingery" spines all around their bodies (sixteen pairs of scoli), and they undergo five larval instars from just over 1 mm to 4-5 mm.
Early instar measuring around 1 mm, and shown with munchie hole:
Middle instar measuring around 3 mm:
Late instar measuring around 4.5 mm:
See
VIDEO of final-instar larva munching on leaf.
See
VIDEO of final-instar larva awkwardly lumbering along, carrying a cumbersome fecal shield at its largest size.
Gratiana pallidula larvae form fecal shields from frass and exuviae attached to their caudal furca or anal fork. Larvae can rest the fecal shields over their bodies or hold them vertically.
Raised vs. lowered fecal shield:
It appears to me that you can count the head capsules on the fecal shield to correspond with the larval instar.
This
VIDEO shows a final-instar larva wandering to find a safe spot to pupate. He lumbers along even while aphids use him as a truss bridge.
PUPA:
Prepupal larvae will sometimes remain on a plant or sometimes wander off of the plant to find a safe place to pupate. It appeared to me that the larvae remain prepupal for two to three days and gradually pupate.
prepupal larva:
pupa at 7 days just before eclosing:
Unlike Deloyala guttata, who keep their fecal shield in the pupal stage, these guys shed the pupal shield with the bare caudal furca remaining at around a 45-degree angle over the body.
Here are dropped fecal shields of prepupal larvae:
pupating Gratiana pallidula, retaining caudal furca:
Pupa dorsal and ventral:
ADULT:
Gratiana pallidula adult next to final-instar pupa:
My pupae generally eclosed in seven to nine days, taking a bit longer than the Deloyala guttata I had raised. Adults are a very pale green and then darken with age.
freshly eclosed adult with exuvia, then showing her still wet wings:
Note that the caudal furca remains with the exuvia:
eclosion of Gratiana pallidula:
freshly eclosed adult, still pale:
Here's a
VIDEO of a Gratiana pallidula taking her first walk right after eclosing.
Here's a
VIDEO of a Gratiana pallidula just out of the exuvia moving about as a new adult.
MATING:
These guys are fairly quick to mate and remain in copula for some time, so it's easy to observe the mating process.
Observations and Articles
These beetles are very gentle, generally calm, and play nicely together.
Larvae of these beetles, as with those of other species, are sluggish and therefore quite susceptible to predation by Pentatomidae, Coccinellidae, and others creatures. The most common predator I saw in the wild was Stiretrus anchorago (Pentatomidae » Asopinae), both nymphs and adults, making lunch of Gratiana pallidula larvae of all sizes.
Stiretrus anchorago nymph eating Gratiana pallidula larva:
Stiretrus anchorago adult eating Gratiana pallidula larva:
In early spring, these guys were quite abundant. In the peak of summer, I saw them less frequently in the wild. But with the abundance of wild Solanum in the area, this is a relatively easy species to find.
A few interesting articles:
General descriptive information on Gratiana pallidula:
Gratiana pallidula
Description of similar beetle (Gratiana boliviana):
Gratiana boliviana Spaeth (Insecta: Coleoptera: Chrysomelidae: Cassidinae)
Description of similar beetle (Charidotella sexpunctata):
Creeping Flecks of Gold and Animated Piles of Frass
Rearing description of Gratiana conformis:
Immatures of Gratiana conformis (Boheman) (Coleoptera, Chrysomelidae, Cassidinae)
Fecal shield articles:
Defensive use of a fecal thatch by a beetle larva (Hemisphaerota cyanea)
Fecal defense: This beetle uses 'overhead sewer system' to ward off (most) predators, Cornell biologists discover
Eggs:
An fascinating article on the position of eggs within the Ootheca of a Gratiana beetle:
An analysis of the fate of eggs of Gratiana spadicea (Klug, 1829) (Coleoptera: Chrysomelidae: Cassidinae) in relation to the position in the ootheca