Hawkmoths all (2016.07.11 [Mon.])

 I think I haven’t heard any complaints about going on and on about caterpillars because I work in at a scientific, more specifically a biology, research environment. But I also know that there are people who dislike lepidopteran larvae, whether they’re in the sciences or humanities; there are even lots of folks who don’t like adult moths. So first I have to apologize for my behavior! Even I get a bit creeped out if I stumble upon a last instar gypsy moth while hiking in the mountains, and as a child I really despised sphingids. But as I learned more about the Lepidoptera (moths and butterflies), I came to understand how they are steadfast vegetarians who grow solely from their intake of plant matter and almost uniformly reject the parasitic mode of nutrition (with a few notable exceptions, such as Epipomponia nawai). From that perspective, the sight of a caterpillar busily munching away at a leaf is almost endearing. For a diligent people like the Japanese, I think the caterpillar should be a well-loved creature (despite the damage it does to crops).

 So, hoping to avoid the mistakes of last year, I bought a large number of morning glories just before spring turned to summer. The leafy vines twined around the trellises on my veranda till they nearly buckled under the weight, while I waited for a brooding death’s head hawk-moth to lay her eggs. I was overjoyed when, in the first week of June, I spotted several larvae, born from a secretly deposited clutch, nibbling at a leaf. It would be some time yet before this caterpillar was large enough to attract the attention of a hungry wasp.

 For several days I did no more than wait and watch. But even the tiniest creatures must fight to survive, and I began to notice my nursery’s numbers declining. I hadn’t caught the perpetrator in the act, but there are a few obvious suspects, including ants and larval mantids. Life is hard in the insect world. So I carefully collected the survivors and secured away them in a breeding cage. This was the contingency for which I had prepared such a great number of morning glory leaves.

 Luckily, one of the members of my group loves caterpillars, and took great care of them. One day, while I was away from the lab, I received a message from her reporting that “It’s molted!” (Fig. 1). But, what was this? It certainly was no Acherontia lachesis. I had been a bit fretful of the possibility, but now there was clear evidence of my error in the form of a smooth orange tail. Acherontia larvae have knobbly green tail. There was no question that what I had been so lovingly raising was Agrius convolvuli, the convolvulus hawkmoth! At least they are both in the same subfamily, and while they may not be as gorgeous as their death’s head brethren, they do sport exquisitely Japanesque black and pink stripes on their bellies. Oh well. After coming this far, I suppose I should continue to let my ugly ducklings bloom.

 Over time, I became fonder of my charge, as its brown coloration deepened and it grew to an almost grotesque size (Fig. 2). The tail turned to shiny black. Just as in Acherontia, convolvulus larvae are polymorphs. Another of my larvae, for example, became a lovely shade of chartreuse (Fig. 3), with a very fashionable yellow tail capped in black.

 This time, to prevent a recurrence of last year’s tragedy, I had laid a layer of soil in the bottom of the cage so that the larvae could begin their pupation without delay. But only half of them emerged from their cocoons in mid-July (Fig. 4). The rest seemed to encounter difficulties in eclosion, particularly in the emergence of the proboscis. Death’s head hawkmoths have shorter haustella, so I suppose they don’t run into the same trouble, but convolvulus hawkmoth pupae have a unique primitive proboscis shaped like a teapot handle, and it seems that it’s liable to defects if disturbed in the pre-pupal stage. Maybe something happened when I handled the larvae, or perhaps they bumped against each other while buried in the soil. Whatever the case, this kind of thing never happens in the pellucid (Cephonodes hylas) or the hummingbird (Macroglossum pyrrhosticta) hawkmoths. What I can say for certain is that it’s not easy raising big moths. And summer still shows no sign of relenting...