Birds most likely to have survived a mass
extinction 66 million years ago would have
been small, able to fly and just fine living on
the ground (as seen in this artist’s depiction).
BY ERIKA ENGELHAUPT
Despite a public debate that grows more
fractious with every school shooting,
Americans actually agree on gun policy
to a surprising extent.
According to a survey of more than
2,100 people, majorities of both gun owners and nonowners support 15 potential
gun restrictions or regulations, researchers report online May 17 in the American
Journal of Public Health.
“There’s much more agreement than
one would think given the rhetoric and
the fighting,” says David Hemenway, an
expert on violence prevention at the
But Hemenway points out that a
dearth of firearms research makes it
hard to predict the effectiveness of indi-
vidual policies (SN: 5/14/16, p. 16). s
HUMANS & SOCIE TY
on 15 gun policies
But there’s division over guns
in schools, assault weapons
These telltale plant substances help
female Microplitis rufiventris wasps
track down a suitable species of caterpillar in which to inject an egg. “Out of
that egg comes a little larva, and it starts
eating the insides of the caterpillar — not
a very pleasant thing,” Turlings says.
Caterpillars continue feeding for several
days but then just passively stay alive
longer as a source of fresh baby food.
What Turlings and colleagues have
found, however, is that what the caterpillar eats makes a difference. Wasps were
more interested in caterpillars grazing
on maize that researchers genetically
engineered not to produce a plant
defense compound called indole. In contrast, wasps weren’t very likely to inject
eggs if this caterpillar species had been
feeding on normal maize leaves.
Indole’s “mothball-like odor [is] terrible in high dosages,” Turlings says.
Caterpillars didn’t like it much either —
except when female wasps were zinging
nearby. Then the caterpillars fed willingly enough, a test showed. “It’s almost
like self-medicating,” he says.
There’s a cost to the caterpillars’
choice to tolerate indole-rich foliage.
“They grow fatter but not healthier,”
Turlings says. More die prematurely.
On the plus side, wasp eggs don’t flour-
ish as well inside these caterpillars if
a wasp does try to use them as zombi-
fied baby food. The odor of pure indole
could attract the wasps, but caterpillars
that bulked up on indole-rich leaves did
not, the researchers found in lab tests.
This caterpillar’s foraging evolution
had found a loophole in maize’s defense
Just about every plant tested so far
synthesizes special compounds that can
lure in some kinds of natural enemies of
pests, Turlings says. Yet he’d never run
across a caterpillar with this bad-food
strategy of avoiding the wasps.
Caterpillars evolving a work-around
defense against a widespread plant
defense isn’t a shock to chemical ecologist
James Tumlinson of Penn State. In these
ornate biological systems of deceit and
manipulation, “pretty much anything you
can think of is possible,” he says. “Once
we get over our surprise, it nearly always
makes evolutionary sense.” s
to reconstruct the most likely lifestyles
of the earliest survivors. These prob-
ably weren’t tree-dependent birds, the
The glory days of dinosaurs had plenty
of flying tree dwellers. So far, paleontol-
ogists have identified at least 80 kinds
of what are called “opposite birds,” the
Enantiornithes (SN: 2/4/17, p. 26). “If
you saw one flying around today, you’d
say, ‘ Well, that’s a bird,’ ” Field says. Their
feet looked like those of birds that perch
on tree limbs, so he’s not surprised that a
fossil of an opposite bird from this prob-
ably arboreal group has never been found
in rock formed after the dino doomsday.
What did happen, however, was that
when trees and forests came back after
the disaster, birds quickly evolved arbo-
real lifestyles again, the team says.
Many people don’t realize that birds
almost died off during the mass extinction, too, says paleontologist Stephen
Brusatte of the University of Edinburgh,
who has studied bird evolution but was
not involved in the new study. What let
the few survivors squeak through, he
says, has been a mystery for a long time.
The whole scenario of a ground dweller’s
advantage and then a return to the trees
“makes a lot of intuitive sense.” s