Lestid Laying Eggs

A few weeks back, I was relaxing after a big science event I had hosted at the museum field station where I work and was taking some photos.  I was sitting on the platforms we have near the pond and watching green darners flying around, looking for some common whitetails and other early spring dragonflies.  I noticed a large spreadwing damselfly on a plant in a strange position and slowly approached so I could get a photo.  This is what I saw:

Spreadwing damselfly laying eggs

Spreadwing damselfly laying eggs

She was laying eggs!  You can see her egg laying tube, her ovipositor, protruding from her abdomen and stuck down into the plant in the photo.  It’s the black pointy bit just to the right of her abdomen just above the plant.  I watched for a little while and saw her pull her ovipositor out of the plant, move down a half a centimeter or so, and stick it back in several times.

Eventually I got distracted by a freshly emerged common whitetail and went over to take some photos of it.  When I went back over to the pond, the damselfly was gone. However, you could clearly see the evidence that she had been laying eggs inside the plant:

Punctures in the plant after the damselfly flew away

Punctures in the plant after the damselfly flew away

I’ve read about spreadwings laying their eggs in plants before, but hadn’t ever seen it. So exciting!  The nymphs that hatch inside plants eventually make their way to the water where they will spend the rest of their childhoods as long, relatively large and robust damselfly nymphs with funky mouthparts.  In this particular pond, few things get much bigger than the spreadwing nymphs, just the frogs, yellow-bellied sliders, and the three monster snapping turtles I saw sunning themselves last weekend.  Always good to know that a pond you regularly get into has multiple gigantic snapping turtles lurking in it…

I’ve got a long list of things I want to share, so hopefully I’ll be able to get another post up soon!

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth.

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Birth of a Backswimmer (Friday 5)

A few months ago, I posted a series of photos for Friday 5 that depicted the development of aquatic snail eggs.  In addition to the two species of snails I had in my tank at the time were a bunch of backswimmers in the genus Notonecta.  The morning after I put them in the tank, I came across a bunch of what could only be backswimmer eggs attached to a leaf, so I started photographing them.  I thought their development was fascinating and spent a little over two weeks watching the snail and the backswimmer eggs to see what happened.  Today I give you the Notonecta part of the story!

The eggs started out looking like what I would consider pretty standard true bug eggs:

Notonecta eggs, 1 day old

Notonecta eggs, 1 day old

They were simple to start off, just translucent white cylindrical eggs with rounded ends.  Many eggs were attached to this leaf in a sort of neat little line along the edges, but there were others attached to rocks and even a few stuck to the large rams horn snail that was oozing its way around the tank, so I suspect this was simply a convenient place to deposit them rather than a preferred method of placement.  In just under a week, some changes were evident:

Notonecta eggs, 6 days old

Notonecta eggs, 6 days old

This photo isn’t as well focused as I’d like, but it illustrates two things.   First, the structure of insect egg shells is absolutely stunning!  All of that patterning mirrors the cells that laid down the chorion (= the insect eggshell), so you’re effectively looking at structure of the mother’s internal organs when you look at an insect chorion.  In both eggs you can also see some faint red markings, more distinctly in the egg on the right.  Those red patches are the developing eyes of the backswimmers, so you can see which end is the head and which is the tail.  What was previously a little cylinder of bug goo had turned into the start of a baby insect with clear evidence of the changes visible without dissecting the egg in just a few days.

Things started to change more rapidly after the first eye spots were visible.  By day 10, the eggs looked like this:

Notonecta eggs, 10 days old

Notonecta eggs, 10 days old

The red eye patches had taken on the shape of backswimmer eyes by this point.  You could also see some black markings within the egg.  The bugs inside were clearly further along than they had been.  You could also easily spot the eggs that were not developing and were never going to hatch at this point.  The egg on the left side of the image was having problems and wasn’t developing properly – it has no eyes or any black patterning visible.  It never hatched.

Shortly before they hatched, you could see all sorts of structures inside the eggs:

Notonecta eggs, 18 days old

Notonecta eggs, 18 days old

You can’t see it very well without enlarging the photo (click to enlarge!), but you can see the outline of the plates on the upper surface of the thorax, the legs, and that the black markings are part of the legs.  By this point, the eggs were two and half weeks old and a few had hatched.  The empty chorions in the lower right corner highlight the cap of the egg the nymph inside popped open to emerge from the egg and a membrane that lined the chorion.  The eggs in this image hatched over three days (if they hatched at all), so they seemed to have some variability in their developmental times.

This is what came out of the egg:

Notonecta first instar

Notonecta first instar

The first instar nymphs were tiny, just a few millimeters long.  You can clearly see the bright red eyes and the black claws, both of which were visible through the egg chorion as they developed.  And, as a bonus this week, this is what these tiny nymphs eventually turn into:

Notonecta mature adult

Notonecta mature adult

The coloration becomes a lot more complex, they gain wings, and their bodies elongate relative to their width as they age.  Check out those gorgeous eyes on the adult!  And, these insects are fairly large, about 1 cm, which means that they have to grow a lot to become adults, and they do it very quickly.  That tiny nymph emerges from the egg and molts just 5 times before it becomes an adult, which means massive growth spurts each time they molt.

I know it probably makes me weird, but I love watching insect eggs develop!  They undergo some pretty amazing changes in a very short amount of time, plus they’re beautiful to look at and you can often see through the chorion and peek at what’s happening inside.  Eggs might not move, but they’re still fascinating and I am thrilled I got an opportunity to document how these eggs developed!  I hope at least some of you find it as interesting as I did.  :)

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth

Well-Nigh Wordless Wednesday: Eggs

It’s blackberry time in North Carolina!  Blackberries all over the Triangle Area are currently laden with ripe fruit, so I went out picking at work before we opened last weekend.  We’d been finding little groups of metallic gold insect eggs all over the grounds for a few weeks, and I found another little group of them while I was blackberry hunting:

Golden insect eggs

Golden insect eggs

The picture doesn’t do the coloration justice at all as these are bright, shiny gold in real life, but I’m sharing them anyway.  After searching around a bit, I believe these are eggs of a leaf-footed bug, an insect in the family Coreidae.  I love it when I randomly come across beautiful bugs when I’m out looking for something else!

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth

Friday 5+1: The Brief Life of a Lethocerus Egg

In case anyone reading this doesn’t know already, a large part of the research I do deals with giant water bug eggs.  I spend a huge amount of my time staring at eggs with an electron microscope, rearing eggs, doing experiments on eggs, grinding eggs up to do chemical analyses, counting eggs…  Perhaps I spend a little too much time with eggs, though I’ll leave you all to decide that on your own.  Giant water bugs have a lot of interesting features to recommend them (including some really beautiful structures on the egg-shell), but I think one feature in particular is especially worth mentioning.  If you know much about eggs in general, such as bird eggs, reptile eggs, or other insect eggs, you probably know that most animals lay their eggs and the embryos develop within the confined space inside.  This isn’t what happens with giant water bug eggs!  Instead, they absorb water (a lot of water!) and puff up the eggshell from the inside so they get bigger over time.  In fact, giant water bug eggs, as big as they are to begin with, nearly double in size between the time they are laid to the time the nymphs hatch and swim away.  Their eggs GROW!  Simply spectacular.

For today’s special Friday 5+1, I’m going to share a series of photos I took of the eggs of the giant water bug Lethocerus medius a few years ago that show how they grow as they develop.  It may a little difficult to see if you don’t spend as much time around these things as I do, but compare the Day 1 eggs to Day 6 eggs and you should be able to see the change clearly.  I’m also going to give you a bit of commentary so you know what to look for.  Let’s start at the obvious place…

Day 1.  Lethocerus medius eggs start off just shy of 3 mm long and about 6 mg, a substantial insect egg.  This species is an emergent brooding giant water bug (see my post about giant water bug child care for more information), so it lays its eggs on vegetation out of water.  As you can see, the eggs are very tightly packed so that most of each egg is touching the others with only a small part of the top free:

day 1 eggs

Day 2. On the second day, things look rather similar from the outside, though the eggs get a little taller and a little heavier:

day 2 eggs

Day 3.  By day 3, the eggs have gained almost half a millimeter in height and 0.2 mm in width.  The weight has gone up too, nearly 2 mg.  You can start to see the eggs bulging at bit at the top:

day 3 eggs

Day 4. The eggs are growing more noticeably now, gaining another 0.5 mm and 2-3 mg overnight!  You can see how the eggs start to crowd each other a bit.  They’re fixed in place at the bottom, but they start to spread out at the top so that they can all fit:

day 4 eggs

Day 5. By day 5, the eggs have stopped growing up and begin to grow out a bit, adding 1/10th of a millimeter and another 2-3 mg in weight.  The eggs are now over 4 mm tall and 2 mm wide and weigh nearly 13 mg! The eggs continue to spread apart at the top end as they increase in size so that you begin to see gaps between the eggs and can start to see the sides of the eggs as well as the tops:

day 5 eggs

Day 6. During their last day in the egg stage, the eggs have topped an enormous 5 mm (that’s HALF A CENTIMETER!  Huge!) in height, nearly 2.3 mm in width near the top of the eggs, and reached 14+ mg!  These are truly big eggs now, and have nearly doubled in height in 6 days.  You can see nearly all the way down to the stick in some of the gaps between the eggs and the eggs themselves look like they’re ready to pop:

If they make it this far, you’ll usually see the following events the same night.  Hatching:

hatching eggs

… and then the newly hatched nymphs swim away, leaving behind only a stick and some empty shells:

hatched, empty eggs

And there you have it!  A wonderful set of growing insect eggs! Lethocerus medius isn’t the only water bug that exhibits this amazing growth either.  Other giant water bugs have shown similar patterns, including a mix of emergent brooders and back brooders.  Growing eggs seem to be quite common, if not universal, within the family to which the giant water bugs belong, the Belostomatidae.  Just one more way that giant water bugs are among the most amazing insects ever!

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

Friday 5: Insect Eggs!

Today’s Friday 5 is going to be shorter and a bit more of a photo album compared to my usual posts.  I work with the eggs of giant water bugs in my research, and if you read my recent post on insect egg anatomy you know there’s a soft spot in my heart for all things insect egg related.  There are some truly beautiful insects eggs out there (if you haven’t seen the National Geographic insect egg article or Martin Oeggerli’s Micronaut website, you should visit both as soon as possible!) and I try to document them when I see them.  Some of the photos are less than perfect, but I take them for myself so I will remember seeing the eggs instead of focusing on producing a perfect image.  Some insect egg photos from my collection:

cactus eggs

Eggs on a barrel cactus spine.

I have no idea what these are, but I wish I did!  The eggs are gorgeous and have some bizarre structures that I would like to look into further.  If you know what these are, I’d love to hear from you!  I found them on a barrel cactus in October.

lacewing egg

Green lacewing egg, hatched.

I actually know what this one is!  Green lacewings lay their eggs on little stalks like these and they’re all over my yard in the summer.  This egg was laid under the porch light where the lacewings like to hang out at night and the larva had already hatched.  I liked the color of the white stalk against the rust colored adobe walls of my duplex, so I snapped a few photos.  Lacking a flash at the time, this was the least blurry.  :)

moth ovipositing on sliding glass door

Moth ovipositing on sliding glass door.

I was sitting on my couch reading one night when I looked up and noticed a moth (likely a noctuid, though honestly I didn’t look that closely) moving around strangely on the sliding glass door to the backyard.  I got up to see what it was doing and noticed it was laying eggs!  I ran to get my obsolete point and shoot digital camera and took the photo from inside the house through the very dirty glass.  This produced a rather cruddy photo.  Still, it makes me smile every time I see it because it was fun to watch the mom laying her eggs on my door.  All of the eggs eventually hatched, so presumably her efforts were worth it!

eggs on strawberry

Eggs on strawberry.

I despise most fruits, but I eat the few I like in massive quantities when they’re in season.  Last summer I was happily working my way through an entire pound of some of the most delicious organic strawberries I’d ever had when I noticed the little cluster of eggs on this berry just before I popped it into my mouth.  Because I’m me, I pondered the beauty of the drab grey eggs against the bright red strawberry for a while and decided it warranted a photograph.  I love how the photo turned out!  I didn’t think to save the eggs to identify them, but I think they’re probably stink bug eggs based on the features I can see in my photos.

Lethocerus eggs hatching

Lethocerus medius eggs hatching

Last but not least, these are some of the eggs I study, laid by the giant water bug Lethocerus medius.  This species is an emergent brooder and lays its eggs above the water line.  The father then carries water to the eggs and protects them until the nymphs hatch.  They are gorgeous, enormous eggs, but they’re even more impressive when they hatch.  The nymphs hatch synchronously, so 200+ little water bugs wriggle their little bodies out the eggs at the same time.  It’s an amazing sight!

I wish more people took a closer look at insect eggs because they are fascinating up close.  There are a ton of different styles and shapes and structures and vary quite a bit from group to group.  They make great photographic subjects too because they don’t move!  I encourage everyone to go out and look for insect eggs around their homes.  And if you get great photos that you’d like to share, feel free to share links on/upload them to The Dragonfly Woman’s Facebook page.  I’d love to see what you find!

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Unless otherwise stated, all text, images, and video are copyright © 2011 DragonflyWoman.wordpress.com

The Anatomy of Insect Eggs

I work with giant water bugs in my research, but the main focus of my work is actually their eggs.  All the behaviors I observe and the physiology I measure are related to the egg stage of their development.  Today I thought I’d give a crash course in insect egg anatomy using my giant water bugs as models.

But first, a quick disclaimer!  Giant water bugs have strange eggs.  The insect developing inside the eggs require parental care and cannot survive without it in the wild (you can get them to hatch without the parents under certain laboratory conditions) and the exact locations of the structures on the eggs you’ll see here are different from many other insect species.  Still, giant water bugs have the same structures as other insect eggs and those structures do the same things for the insect developing inside the egg as they do in other species.  Just remember that parental care of eggs is rather rare in insects, and the paternal parental care of the giant water bugs barely exists outside their group.

Okay, first things first!  Let’s start with a cluster of eggs:

Abedus herberti

Abedus herberti

Some insects lay their eggs in clusters and others will lay them one by one and really spread them out.  Water bugs lay in clusters so you can see the cluster of eggs where it has been laid: on this male Abedus herberti’s back.

If we zoom in a bit closer, we can start to see what the eggs look like:

Abedus eggs

Abedus herberti eggs, up close!

Abedus herberti eggs happen to change in structure about halfway down, so that’s why you can see the brown change to grey in the photo above.  Some insects do this, others do not.  Regardless, the shell of insect eggs has a special name: the chorion.  Let’s zoom in a bit more and get a good close look at the chorion on the top of the egg:

Abedus egg top

Abedus herberti egg top

This image was taken using a scanning electron microscope (SEM) so that you can get a VERY close look at the structure of the chorion!  This egg was mounted onto an SEM stub upright so that you are looking down at the top of the egg here.  Notice the area indicated by the arrow.  That area is called the micropylar region.  If you look very closely at the image (you can click on it to make it bigger), you can see little white marks within the micropylar area.  Those lines represent the micropyles:

micropyles

The micropyles

Eggshells are meant to contain the animal growing inside them and protect them from the environment.  If anything needs to get into or out of an egg, it has to go through the shell.  That’s where the micropyles come in!  Female insects produce the eggs, but the chorion is deposited before the eggs are fertilized.  Sperm have to get inside the eggs to fertilize them and have to go through the shell to do so.  They enter through the micropyles to pass through the chorion to the egg waiting inside.  The arrow in the photo above shows one micropyle within the micropylar region of Abedus herberti.  There is a second micropyle to the left.  This species has anywhere from 2 to 7 micropyles arranged in an arc, but other insects have different numbers and arrangements of micropyles.

Let’s zoom back out a bit and take a look at the structure of the top of the egg again:

Abedus egg top,showing aeropyles

Abedus herberti egg top

In this image you can see the fine structure of the chorion and see all the little polygons that cover the surface of the egg.  Many insect eggs exhibit raised polygons similar to the ones you see in the Abedus herberti egg.  These are an artifact of the chorion production process in females.  I’m not going into it now because the process by which insects produce eggs is long and involved and better suited to a series of posts (I wrote 19 single spaced pages on this subject as part of the written part of my Ph.D. comprehensive exams!), but those polygons represent the shape of cells that are involved in building the chorion and they’re visible on many insect eggs.

The embryos developing inside the egg need oxygen to survive, but they have to get it from the atmosphere outside the eggshell.  That means the oxygen has to cross the eggshell before the embryos can make use of it.  Sperm enters the egg through micropyles.  Oxygen enters through aeropyles.  The arrow in the image above points to an aeropyle on the chorion of Abedus herberti and you can see several of them dotting the surface of the egg.  I think they look rather like lunar craters!  Let’s take a closer look at an aeropyle:

aeropyles and plastron network

Aeropyles and plastron network

The two holes in the center of the image are aeropyles, little holes in the chorion that allow the embryo inside to get the oxygen it requires.  The exact path oxygen takes from the atmosphere to the developing insect is a little complicated and probably varies from species to species, but the aeropyles are where the path begins.  The number and arrangement of the aeropyles varies across species quite a bit.  Some insects have them distributed across the entire chorion.  Others keep them localized in specific areas (Google “pentatomid eggs” for some good examples).  Many aquatic insect eggs don’t have aeropyles at all and depend on oxygen flowing directly through the shell.  Some aeropyles have sieve-like covers over the opening and others are just big gaping holes like the ones you see in the image above.  There’s a lot of variation, but they all share a common goal: allowing oxygen to enter the egg.

Did you notice that the area within the polygons near the aeropyles looks kinda spongy in the image above?  That’s because the eggs in this species have a structure called a plastron network.  Plastron networks are meshworks made up of many tiny projections of the chorion.  This meshwork is thought to trap air against eggs when they are underwater so that they don’t drown.  Many terrestrial eggs have these plastron networks and this structure may allow them to survive accidental submersion for some time.  Water bugs also usually have plastron networks that may be responsible for their survival while they are underwater.  Lots of other aquatic insects that lay their eggs in water don’t have these structures at all.

The structures I mentioned above are the typical structures you find on most insect eggs.  However, you can find other structures depending on the species.  Giant water bugs absorb water from the environment and the water passes through a structure at the base of the chorion called the hydropyle.  A few other insects have hydropyles.  Other species will have structures to keep their eggs in place once they’ve been laid.  Still others might have horns or other structures that allow them to respire more efficiently.  Just like the animals growing inside them, insect eggs show a lot of variation in color, structure, and arrangement of the structures and can differ a lot from species to species.

I’m still taking entries for my contest for a few more days!  If you want to win the mug, be sure to leave a comment here for your chance.  The winner will be announced Wednesday.

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Unless otherwise stated, all text, images, and video are copyright © 2011 DragonflyWoman.wordpress.com