Life Cycle – Red-headed Chrysomela leaf beetle

A red-headed Chrysomela leaf beetle (Chrysomela texana).

These  red-headed Chrysomela leaf beetles were all over the park near my home this week, mostly in the vicinity of a large willow tree, the beetles’ food of choice.  Chrysomela texana are close relatives of the cottonwood leaf beetle (Chrysomela scripta).   C. texana can be easily distinguished by it’s red pronotum, head, and underside (most similar species have distinct black markings on these areas).  Every life stage of the beetle was apparent, from the yellow eggs laid in clusters on a leaf, to the lady beetle-like black and brown larvae, skeletonizing the surrounding vegetation in gregarious clusters, the red-brown pupae.

A cluster of yellow red-headed Chrysomela leaf beetle eggs on the underside of a leaf.

(Note: The egg hunt was successful.  Happy Easter!)

A gregarious cluster of red-headed Chrysomela leaf beetle larvae skeletonize a willow leaf.

Like swallowtail caterpillars, the larvae have cool, eversible glands which they use to secrete defensive chemicals (as pictured by Mike Quinn on BugGuide).  The pupae of these beetles were particularly abundant.  They seemed to be stuck to every surface I looked at–tucked under bark, into crevices, dangling from leaves and even from small flowers and weeds.  This gave me the chance to snap the pictures below of a beetle struggling out of its pupal case. I even took a few home, but they were sneaky and eclosed on me when I wasn’t looking.

A red-headed Chrysomela leaf beetle (Chrysomela texana) ecloses from its pupal case.

A red-headed Chrysomela leaf-beetle ecloses from its pupal case.

Cast off pupal case of a red-headed Chrysomela leaf beetle.

*edit*

Surprise bonus image!  Now the life cycle is complete. 😉

A mating pair of red-headed Chrysomela leaf beetles (Chrysomela texana).

Casebearers

A case-bearing leaf beetle laravae (Chrysomelidae: Cryptocephalinae)

Anyone noticing one of these small brown objects on a leaf could easily dismiss it as bird droppings.  Only a close look will reveal their secret–these cases house hungry beetle larvae, who can munch on the leaf in the security of their protection and disguise.  For my own part I only discovered these insects when I took a closer look at some of the contents of my sweep net.  They seem to be relatively common in Texas in the late spring as I turned them up frequently at a number of field sites.

These insects are a type of leaf beetle (family Chrysomelidae), belonging to the sub-family Cryptocephalinae (literally “hidden head”), the case-bearing leaf beetles, or casebearers.  (For those not up to date with Latin naming conventions, the “-dae” suffix is used to indicated families, and the “-nae” suffix is used for subfamilies.)  The ‘case’ is a gift provided by the mothers–they wrap the eggs in layers of fecal matter, which the larvae later add to.

Pretty Plumes

Gregarious insect larvae eating a leaf in Argentina.

These little guys were tiny enough to overlook easily, but bizarre and striking on close inspection.  I am informed that the peacock like ‘plumes’ on the ends of these insects are likely to be made from cast skins or even ‘tubes’ of excrement.  The beauty of nature.

A chrysomelid larva on an arm.

Insect larvae can be tricky to identify, but general consensus among entomologists I showed this to, is that these are some sort of chrysomelid (leaf beetle) larvae.  The family Chrysomelidae is a large and diverse group of small to medium sized beetles which take on a variety of forms, but tend to be found feeding on plants in both the larval and adult forms.  These particular larvae appear likely to be skeletonizing leaf beetles*, so named from the manner in which they feed off the plant, and the leaf ‘skeleton’ left behind.  Like many insect larvae, these appear to be somewhat gregarious, as I observed them mostly in small groups.

Two chrysomelid larvae with dimorphic coloration.

*Update:  Laura suggests that these should be Cassidinae, or the larvae of tortoise beetles (see comments).  Tortoise beetles are fabulous little critters, so I’m thrilled to learn that their babies frequently make dramatic poop structures.