Scientist Love: “Mothering” a Brood of Mantids

by Deepa Rajan – I woke up on a Sunday morning in late September to an urgent text from my friend, Harshith, about a hatching. He had found an ootheca (egg-casing) in a tree a couple of weeks prior and had since been incubating the specimen in a 50 mL conical centrifuge tube. I kept watch on the ootheca as well, unsure of whether it would hatch, or when. But on this particular Sunday morning, I rushed to Harshith’s room and beheld the sight of tiny mantids emerging from the surface of the ootheca. The nymphs (immature mantids) had just been hatching for a couple of hours when I arrived on the scene, but about a hundred were crawling about in the conical tube by the end of the day! They were so small and agile with such angular limbs that they almost seemed like miniature automatons rather than living creatures. Harshith did not want to keep the nymphs and planned to release the insects if I did not want to take care of them myself but, of course, at this point how could I let go of such curious critters? And thus began my journey with the mantids. I felt like a mother! A hundred little lives now depended on me for their survival, and it was a beautiful burden that I felt unqualified but honored to bear.

As their numbers increased, Harshith and I split the nymphs into two separate containers to avoid overcrowding and facilitate observation. Their big, black eyes appeared especially prominent against their bodies of bright green, a hue which reminded me of a cherished Robert Frost poem:

               “Nature’s first green is gold,

               Her hardest hue to hold.

               Her early leaf’s a flower;

               But only so an hour.

               Then leaf subsides to leaf.

               So Eden sank to grief,

               So dawn goes down to day.

               Nothing gold can stay.”

And, sure enough, the nymphs traded their nascent green for a darker, brownish color within only a day. The swiftness of the color change intrigued me and I thought about the myriad biological processes that must have contributed to the transformation within a mere few hours – perhaps the translation of a new pigment molecule? Or the development of new internal structures that obscured the apparent lucidity of the initial light green?

I placed a few nymphs under the microscope for a closer look. I quickly realized that the mantids were too fast to stay in one place for observation, so I put them in a petri dish filled with water to slow them down. I suppose it was at this moment when I realized that a mother’s love is different from a scientist’s love. A mother would obviously have qualms about drowning her children for ease of studying their anatomy (unless we are discussing mantis mothers, which often eat their children for extra nutrition). However, as a scientist, I just wanted to look closely at these mantids and learn more about them. Under the scrutinous lenses of a light microscope and a human eye attuned to beauty, the intricacies of these creatures became more discernible. I noticed the subtle stripes on the legs, the fluid moving through the semi-transparent bodies, the varying numbers of abdominal segments (eight for male, six for female), the occasional broken antenna, the ommatidia of the large compound eyes with dark pseudopupils. Is looking at and knowing something deeply the same thing as loving it? I am not exactly sure, but I think they go hand in hand. The more I looked at the mantids under the microscope, the more difficult it was for me to make the first cut of the dissection I was itching to perform. Slicing through the thorax of a nymph might have been easier – on a sentimental level, not technique-wise – had I done so under only my naked eye rather than under the microscope because beneath such a meticulous lens, every movement, the wriggling and thrashing about in the water, each turning of the head and claw at life became visible to me. After witnessing the organism in such an intimate way and subsequently loving it more by nature of knowing it on a deeper level, the nymph seemed infinitely more vulnerable under my blade.

IMG_0502

by Deepa Rajan

The microscope also set center stage for the tiny, parasitoid wasps that materialized from the mantis ootheca almost simultaneously with the nymph emergence! Harshith told me that the wasps started crawling out only a couple of hours after the mantids began hatching, although the wasps were so small that I barely noticed their presence. An adult female wasp must have laid her eggs within the ootheca, allowing her own offspring easy access to their first meal upon emergence: mantis eggs. Of course, the newly hatched wasps obviously did not eat all of the mantis eggs because dozens of nymphs still managed to emerge from the ootheca. I first assumed that the wasp was black in color but once I increased the magnification, the large red eyes and the iridescent emerald green of its exoskeleton became apparent. The outer surface had such a unique visual texture that it gave the impression of an insect studded with hundreds of miniscule, glittering diamonds.

Picture2

Podagrion wasps emerging from a mantis ootheca. Photo by OZWILDLIFE, Copyright 2007 (http://www.ozanimals.com/Insect/Mantis-Parasitic-Wasp/Podagrion/sp.html)

I turned to the internet and determined that the parasitoid wasps belonged to the Podagrion genus. Females of this particular species possess long ovipositors which they use to insert their eggs within a mantis ootheca. Sure enough, I noticed dozens of wasps dragging whip-like projections dangling like tails around the conical centrifuge tube. I considered removing the wasps or at least separating them from the nymphs in case they posed any threat to the young mantids, but I was also curious to find out what would result from their cohabitation so I allowed the wasps free range. They were simply stunning. I could not help but love the (former) predators of my charges as much as the charges themselves.

Picture1

Podagrion wasp. Photo by Nicky Bay, Copyright 2013 (https://www.flickr.com/photos/nickadel/9291107953)

After I was satisfied with my examinations of the mantids and their parasitoids, I transferred them to a mesh cage along with the original ootheca. I sprayed water in the cage daily and, since mantids only feed on live prey, released fruit flies left over from lab experiments into the enclosure. The wasps died after some time and so did several dozen nymphs, possibly due to their sheer numbers and close proximity, but quite a few mantids persisted. I became privy to their mannerisms: the gentle swaying back and forth while hanging onto the mesh fabric of the cage, the ever-improving agility with which they used their front legs to capture the fruit flies, the munching of mandibles relishing fruit fly bodies while the red-eyed creatures still wriggled their legs in protest, the way they often let the wings drop to the floor, littering the paper towels I had enclosed with speckles of gray, the unusual sluggishness and disregard of fresh food prior to each molting period. I watched these nymphs molt several times, gradually transforming before my eyes and leaving whitish exoskeletons in their wake. Stripes disappeared, splotches of pink cropped up against the green, and some mantids inevitably grew larger than others.

At around this time, I began witnessing instances of one sibling devouring another. Over the following several weeks, their numbers dwindled to around five: four females and one male. I rarely caught them eating each other but I inferred as such because each day another insect would be gone with no carcass to account for. Although I had selfishly hoped that at least one male and one female would survive to adulthood so that I might behold their unusually violent mating behavior (the female often eats the head of the male – leaving the body still mobile – prior to copulating in part because the additional nourishment helps her produce eggs), the four female nymphs were all larger than the male and ate him.

And now, as we approach mid-December, only one mantis remains. She is beautiful, healthy, and larger than the entire ootheca from which she and her hundred siblings once emerged. I fed her an iridescent wasp the size of half my index finger just yesterday and she savored the ample meal for hours. I have come to understand that I am not a “mother” to this wild insect, nor is she my pet. I am just a humble scientist at the feet of a special creature, observing its nature with fascination and awe. And when this mantis molts for the last time in a few months and finally becomes an adult with a nascent pair of wings, perhaps I will open up the cage to the outside world and let her spread them.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: