CSI Special Insects Unit: Forensic Entomology


Here’s a fascinating niche science that, if you ask me, we should see on prime-time TV way more often: forensic entomology, the study of insects and arthropods used in legal investigations. As it turns out, there are lots of cool ways insects can help us solve crimes. Fair warning, though: you may not want to watch this one over lunch! [music/intro] The field of forensic entomology is
actually pretty broad and is commonly divided up into three general areas: urban, stored product, and medico-legal. The urban specialty focuses on insects in human dwellings. Scientists who do this kind of work
could surely tell you all kinds of amazing things about what goes on in
your kitchen cabinets at night, but as forensic experts, they specialize in
investigating both civil and criminal cases helping in lawsuits involving, say, damages from a cockroach or bed bug infestation. Stored product entomology, meanwhile, usually deals with the contamination of commercial products, like if you find a
family of dead ants in your fast food burrito, or a bunch of moth wings in your candy bar, or spiders in your toilet paper roll. But
the medico-legal area is the most flashy, popularized part of the field. It’s what you might see on an episode of CSI and it often involves reading the signs of blood sucking or carrion-feeding
insects at violent crime scenes typically involving murder, suicide, abuse, and neglect. At a fresh crime scene, for example, forensic entomologist would know that tiny flecks of what look like spattered blood could actually be the prints of roaches
or flies that had walked through blood elsewhere at the scene. These experts can even match human DNA from the blood found in blood feeding insects, living or dead. One murder case in Italy was solved when investigators scraped a blood filled mosquito off the wall in a
suspect’s house and found it contained the blood of the victim. Take that, bad guys! Crime-solving, bug-loving scientists are also often called upon to help estimate a victim’s time of death. A dead body goes through a whole series of phases from putrefaction and
fermentation to dry decay and skeletonization, and each phase attracts different life
stages and types of insects. Forensic entomologists use this rotating cast of critters to help determine a body’s death in a couple of ways usually involving larval development and species succession. The larval development technique studies the size and
prevalence of maggots and other larva and is usually useful if the body is less
than a month old. If the corpse is older, it’s best to use the species succession
method. For example, blow flies are great quickly discovering dead meat because they like their food fresh and full of fluids, so determining what phase they’re in can often provide the most accurate estimates for time of death, but as the flesh dries out the blow flies
take off just as other species like the coffin fly arrive in force. Once the corpse is too dry for even
maggots, all the flies clear out. Then beetles often roll in. Some species like hide and carrion beetles have robust mouth parts they can work on the remaining
dried flesh and ligaments. Mites and moth larvae round out the final cleaning crew, consuming the remaining hair and leaving only a skeleton. So thanks to all the insects out there and
the scientists who study them for solving crimes and doing a job I would rather not do! And thanks for
watching this SciShow Dose especially to all of our subscribers on Subbable who make this whole channel possible. Did you know that you can be an honorary associate
producer of SciShow or even pick the topic for one of our episodes? To find out how you can go to subbable.com/scishow and you can always find us on Facebook and Twitter and if you want to keep getting smarter with us, don’t forget to go to youtube.com/scishow and subscribe! [music]

The Age of Giant Insects

The Age of Giant Insects


This episode is supported by The Great Courses Plus Even though we often refer to this time in
history as the Age of Mammals, we should probably be calling it the Age of Insects. Because, just looking at the numbers, there
are way more of them than there are of us. Humans alone number more than 7 billion at
this point, which is … a lot. But insects? Try 10 quintillion! We may like to think we’re in charge because
we make the rules and, well, we’re bigger than they are. But insects, and other arthropods, weren’t
always so small. About 315 million years ago, they were not
only abundant. They were … enormous. To meet the biggest invertebrates to ever
crawl across the Earth, we have to go back to the Carboniferous Period, from 298 million
to 358 million years ago. That’s when you’d find the likes of Meganeura. It was a griffinfly, a giant relative of today’s
dragonflies, that had a wingspan of about 70 centimeters. That’s about the size of a pigeon — more
than three times larger than the biggest living dragonfly. Meager by comparison was Stephanotypus, another
griffinfly that was still some 40 centimeters across, about as big as a robin. And this greatness in size wasn’t limited
to insects! You see out-sized arthropods all over the
world during this period… like Arthropleura. You know those cute little millipedes you
find curled up under rotting logs in the woods? Now imagine one of those about two meters
long and a half meter wide, shuffling like a living carpet over the undergrowth. It was probably the largest arthropod that
ever walked on land. So. What allowed these invertebrates to get so
big? The answer … is oxygen. Take a deep breath. Right now, the amount of oxygen in atmosphere
is about 21 percent. But back in the Carboniferous, it was nearly
35 percent! That’s because the Carboniferous was a time
of incredible, runaway plant growth. Huge forests full of ferns, mosses, and some
of the earliest vascular plants had taken over much of the planet. They sucked in carbon dioxide and pumped out
oxygen in enormous amounts. Now, you might be thinking: Earth has lots
of trees now. So what’s the difference? Well, today, that big log you find in the
woods with all of those bugs under it? That log is being decomposed by bacteria,
among other things, that take in oxygen, and release CO2. But in the Carboniferous, those wood-eating
bacteria didn’t exist yet. So Earth’s giant, primordial forests were
taking in lots of carbon dioxide and pumping out lots of oxygen. That’s what plants do. But since the trees weren’t decomposing,
the CO2 wasn’t being released back into the atmosphere. The result was an all-time high in the world’s
levels of atmospheric oxygen. And that’s what made giant arthropods possible. Because, arthropods don’t breathe the way
we do. They have a system of external openings called
spiracles, that lead to a branching network of tubes called tracheae, that diffuse oxygen
through their bodies. And this puts a limit on their body size. Arthropods can only get so big before they
can no longer draw enough oxygen from the air. But in the Carboniferous, the abundance of
oxygen in the atmosphere made it easier for arthropods to get the O2 that they needed,
which allowed them to reach record-breaking sizes. In fact, paleontologists have managed to make
this happen today in the lab, by experimenting with modern insects. By raising dragonflies, beetles, and other
insects in controlled, oxygen-rich enclosures, scientists at Arizona State found that successive
generations of arthropods can grow faster and larger. But, of course, it’s possible to get too
much of a good thing. So, some scientists have proposed another
theory — that arthropods got huge not because they could, but because they had to. Lots of oxygen might have been a beneficial
for grown-up arthropods, but it also could’ve posed a threat to their larvae. Young invertebrates can’t control their
intake of air like adults can, and too much oxygen can be deadly. So researchers at Michigan State have suggested
that ancient arthropods began producing bigger larvae, so they’d take in less oxygen relative
to their body size. And those bigger larvae resulted in bigger
adults. But, you know enough about natural history
at this point to know that even the biggest creatures don’t stay on top forever. About 275 million years ago, during the Permian
Period, the world changed, yet again. The levels of atmospheric oxygen started to
plummet — why, we’re not sure. Ancient climate shifts might’ve had something
to do with it. But as oxygen levels fell, the interiors of
the world’s continents got warmer. This shrunk the big swamps that were acting
as natural carbon sinks. So, swamps weren’t pumping out as much oxygen
as they used to, and, on top of that, decomposers finally appeared that were able to start breaking
down all of the dead wood. As these microbes took in oxygen and released
carbon dioxide, global levels of O2 dropped even more. And with less oxygen available, it became
increasingly hard for the giant arthropods to survive. By about 305 million years ago, the two-meter-long
Arthropleura could no longer be found on the forest floor. By 299 million years ago, the last of the
Meganeura had flapped its wings. The arthropods that followed never got quite
as spine-tinglingly large as their ancestors were. But, of course, everything turned out fine
for them! Today, we’re totally outnumbered, both in
biomass and in diversity, by insects, arachnids, and other land-based arthropods. But if there ever was a time that was a true
Age of Insects, it was probably the Carboniferous Period, when arthropods of all kinds were
living large. Thanks to the The Great Courses Plus for sponsoring this episode. The Great Courses Plus is a digital learning service that allows you to learn about a range of topics from educators including Ivy league professors and other educators from around the world. Go to TheGreatCoursesPlus.com/Eons and get access to a library of different video lectures about science, math, history, literature, or even how to cook, play chess, or become a photographer. New subjects, lectures, and professors are added every month, like the Introduction to Paleontology series taught by Professor Stuart Sutherland. You can learn about everything from Earth’s shifting crust to Taxonomy and more! With The Great Courses Plus, you can watch as many different lectures as you want – anytime, anywhere without any tests or exams. Help support the series and start your free one month trial by clicking the link below or going to TheGreatCoursesPlus.com/Eons What do you want to know about the story of
life on Earth? Let us know in the comments. And don’t forget to go to youtube.com/eons
and subscribe! If you think dragonflies are fearsome, wait till you see their babies. Our friends at Deep Look filmed them shooting out their super-fast mouthpart to catch a meal. Check it out here.

Bugs Eating Bugs Up Close | Insects, Bugs & Scorpions | Love Nature

Bugs Eating Bugs Up Close | Insects, Bugs & Scorpions | Love Nature


To all the different kinds of bugs that live here, the
forest is a giant buffet. (optimistic music) This giant grasshopper is a herbivore. It has the basic insect tool
kit, three sets of mouth pods. It uses sideways slicing jagged mandibles like scissors to cut up leaves. The other two sets carry jaungent
palps that taste the food, before the grasshopper bites into it. This multi-blade, Swiss
Army knife of tools, evolved from primitive legs and with a few minor modifications can be used to tackle many different
items on the insect menu. This African ground beetle is a carnivore. It hunts on the forest floor but it won’t be a high speed chase. It hunts slugs. These defenseless mollusks seem to just wait to get captured. The beetle’s mandibles have pointed tips, more like curved daggers
than scissors perfect for piercing the gelatinous
slug and dragging it off. (anxious music) The mandibles also serve as steak knives. Below the pointed tips, sharp blades chop up slight meat
into bite sized pieces. (eats loudly) Covered in slime, there’s
no elegant way to eat a slug but the little African
ground beetle is no slob, keeping it’s mouth parts and legs clean is vital to its survival. So after it finishes a meal it finds a napkin to wipe itself clean. This bit of leaf will do nicely. Grasshoppers and beetles
use the insect equivalent of knives and forks to cut
and then chew their food. This stealthy assassin bug
prefers to stab and suck. All three sets of mouth
parts are molded into a long sharp beak, or rostrum. Strong enough to puncture
the armor of its prey, in this case, a wandering cockroach. (foreboding music) The beak is hollow. When it pierces the
roach’s tough exoskeleton, it injects a deadly fast-acting poison which dissolves the prey from the inside. Then, with straw already inserted, the assassin bug slurps up
the gourmet cockroach soup. (slurping) This South African rock scorpion isn’t an insect, it’s an arachnid so it starts with a
different basic toolkit. One set of primitive
legs has been transformed into giant claws called pedipalps evolved to grab and hold the
prey using brute strength, though it’s a bit of overkill
on a little wood louse. (creepy music) Scorpions don’t have mandibles, instead, another much
smaller pair of claws, the chelicerae, reinforced
with heavy metals for toughness tear and shred it’s meal before passing morsels into it’s
mouth hidden from view. All arthropod mouth parts
started out as primitive legs but evolution as transformed
those basic jointed limbs into different structures,
from claws to straws. It’s just one of the reasons
for their incredible success.

Roly Polies Came From the Sea to Conquer the Earth | Deep Look

Roly Polies Came From the Sea to Conquer the Earth | Deep Look


Pill bugs…… roly polies….. potato bugs… whatever you want to call them, somehow there’s something less creepy about these guys than other insects. More loveable, or something. Maybe it’s because they’re not insects
at all. Pill bugs are actually crustaceans. They’re more closely related to shrimp and
lobsters than crickets or beetles. Pill bugs even taste like shellfish, if you
cook them right. Some adventurous foragers call them wood shrimp. As early as 300 million years ago, some intrepid
ancestor crawled out of the ocean, sensing there might be more to eat, or less competition,
on dry land.” But unlike lobsters, pillbugs can roll up
into a perfect little ball for protection. If you look closely you can see the evidence
of where these guys came from. Like their ocean-dwelling cousins, pill bugs
still use gills to breathe. True insects — like this cricket — use a
totally different system. See those tiny holes on this cricket’s abdomen? They’re called spiracles. They lead to a series of tubes that bring
fresh air directly to the insect’s cells. But pill bugs don’t have any of that. To survive on land, they had to adapt. Their gills, called pleopods, are modified
to work in air. Folds in the pleopod gills developed into
hollow branched structures, almost like tiny lungs. In a way, the pillbug is only halfway to becoming
a true land animal. Because… they’re still gills. They need to be kept moist in order to work. Which is why you usually find pill bugs in
moist places, like under damp, rotting logs. They can’t venture too far away. Sure, pill bugs look like the most ordinary
of bugs. But they’re much more than that: evidence
that over evolutionary time, species make big, life-changing leaps. And those stories are written on their bodies. Hey, while we’re on the subject of oddball
crustaceans… check out this episode about mantis shrimp. Their eyes see colors we can’t even
comprehend. Their punch is faster than Muhammad Ali’s. And while we have you: Subscribe. OK? Thank you! And see you next time.