Umber Skippers Pupate & More Cocoon Building

Two of our umber skipper (Poanes melane) caterpillars pupated today! Also, another caterpillar has begun building a cocoon. 

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It took five days of waiting since the first cocoon was spun for it to happen, but it finally happened -- the first two of our umber skippers (Poanes melane) have pupated. With the first individual, we could tell because the silk of its cocoon is very thin and the dark color of the chrysalis underneath can be easily detected. In fact, the cocoon is so loose that all we had to do was pull off a blade of grass out from it in order to expose the chrysalis for our observation. 

The second individual to pupate was never really in a cocoon at all. What we believe happened was that the caterpillar had already started spitting silk in the container with the rest of the caterpillars that are still feeding so when we removed it, it was already very late into the prepupal stage that it could not build a cocoon anymore. For the last few days, it has basically sat in very thin silk mat formed on top of a few grass blades as an immobile prepupa. Because this one pupated later than the individual shown above, it was still teneral when we took pictures of it; it still looks (and felt) slightly wet and soft and the color is much darker. 

Since this is first time we have ever seen umber skipper chrysalises, in real life or elsewhere, we spent quite some time marveling over these two. They are decently large (for a skipper, that is), almost the same in size and mass as a full grown caterpillar (they don't shrink much). At first glance, they look very much just like any generic moth pupa because of the dark earthen color and the lack of major ornamentation. However, they are, of course, actually shaped quite like other skippers. Like other skipper species we have raised, the chrysalises have the chracteristic bulging eyes that create a squarish head and have an overall very elongated, cylindrical shape with a pointy cremaster.  Interestingly, they have freckles along the back and just the slightlest amounts of hair (fuzz!) just like common chekerspot skippers (Pyrgus communis). 

What really caught our eye with these chrysalises though was the proboscis piece. This piece is actually detached from the rest of the pupa and is extremely elongated such that it reaches all the way across to the end of the abdomen like a very long needle! When we have observed umber skipper adults nectaring, we have never really took note if their proboscises were especially long, but this makes us think that they must be. And apparently, a long proboscis on the chrysalis is quite common among grass skippers (Hesperiinae). For what particular reason, we do not know as they seem to suck on a large variety of what seem to be fairly ordinary nectar flowers. The way that the chrysalises are shaped reminds us a lot of the pupae of some feeding sphingids (Macroglossinae) that also have very long proboscises that are detached (partially). 

On another note, we had another fifth instar that finished building a cocoon today. We took this one very early on, as soon as we realized that it was ready so it hadn't wasted any silk before we took it out which could explain why its cocoon is so well formed. It is much larger and more structured than what the other two individuals produced. Seriously, it actually looks like a cocoon! There is a lot of the waxy substance incorporated into the silk, which came from storages on the undersides of the last to abdominal segments on the mature fifth instar. The stuff allegedly helps to keep the cocoon waterproof. 

- Brian