A few days ago, while returning from a walk, I chanced to observe a
dead grasshopper upon the dirt at the side of the road. Now this
incident would not have been of special importance had I not
discovered, upon careful _post-mortem_ examination, the very
remarkable manner of the insect's death, which recalled a similar
surprising episode of several years ago which I had almost forgotten.
Upon referring to my note-book of that period, however, I found
considerable space devoted to the incident, which greatly astonished
me at the time. Inasmuch as it presents in a startling light the
wonderful and strange resources by which nature holds in check the too
rapid increase of species and maintains the great law of equilibrium
among the insect forces, it is well worth recalling in these pages,
in the firm belief that my young entomological readers will henceforth
look more compassionately and tenderly upon the poor "high-elbowed
grig" who is the unfortunate hero of my story. He is familiar to us
all, that hovering "rattler" above the hot, dusty road of August,
flying up from nowhere beneath our feet in the path, fluttering like a
yellow moth, and always disappearing before our eyes when he alights.
He is also known as the "Quaker," from his drab suit and bonnet, and
his generosity with his "molasses" is proverbial from the days of the
Pilgrim settlers. Who would have believed that such a fate as the
following lay in store for him.
In previous papers I have indicated some of the remarkable pranks
which the various ichneumon-flies play with unsuspecting caterpillars.
The polyphemus, for instance, whose cocoon, filled with hopes of a
beautiful butterfly existence, yields only a swarm of wasps. The
caterpillars are helpless, and would seem an easy prey to the wily fly
who lays her eggs upon them; but even the agile-winged "Quaker," and
doubtless many of his kind--yes, and still more agile insects--are not
quick enough to escape a like fate.
At the time of my discovery I had in preparation an article for
"Harper's Magazine" entitled "Among Our Footprints." I wished to
describe and illustrate a singular battle which I had shortly before
observed between a large red mutilla ant and a "Quaker." The mutilla I
had captured at the time, and had preserved as a specimen. I needed
only the grasshopper to complete my drawing. Directly in front of my
city house a number of vacant grassy lots offered a favorite haunt for
the insects--I used to call it the Quaker camp-meeting ground--and I
started out to procure one. Having no net, I was soon convinced that I
was greatly at a disadvantage. The thermometer was about 90 deg., and, of
course, the "Quakers," being in their element, had much the best, not
to say the easiest, time of it. I at length gave up the chase, and was
about leaving the field, when fortune favored me by the discovery of a
clumsy specimen, which seemed unable to fly for any great length, and
he was soon captured. Upon examination his wings seemed partially
paralyzed, but otherwise he appeared to be in good health and spirits,
his hind legs being especially lively and snappy. I immediately took
the insect to my studio, and pinned him through the thorax. He was
strong enough to pull out the pin from the board and jump around the
room with it in my temporary absence.
I lost no time in taking his portrait, which figured in the
illustration to the article on "Footprints" as "the ungainly victim,"
I little dreaming when I gave him such a title what a remarkable sort
of victim he even then was. The drawing took me about ten minutes. I
then left the studio, and was absent precisely fifteen minutes. Upon
returning I found the grasshopper dead.
My curiosity was aroused, not only by such a rapid demise (for the
impaling through the thorax is not usually an immediately fatal injury
to an insect), but especially by some very strange and unnatural
automatic movements of the victim--head protruding and turning from
side to side; queer expansion of body, as though breathing; unusual
lifting and other motions of legs, particularly of hind legs; the
whole demonstration a mockery on life. The grasshopper was pinned to
my drawing-board, and against a piece of newspaper. As I watched his
strange antics, I suddenly discovered that he had become a veritable
phantom of his former self; that I could actually _read the newspaper
text through his body_. Examination now revealed the mystery. I could
easily see every nook and cranny of the grasshopper's interior, so
glassy were the walls of the body, and I could now count about a dozen
small, white larvae, which were now full grown, and were crawling about
within through head, thorax, body, and hind legs, cleaning its walls
of every particle of remaining tissue, and causing the singular
motions described. Such a strange house-cleaning I never saw before.
When the "Quaker" locust was captured it showed not the slightest sign
of any such goings-on within its being. The final voracity of the
larvae was swift and terrible. And what an astonishing instinct is that
which should teach these parasites to avoid the vitals of their insect
host until the last moments of their own final, complete growth! The
entire space of time from the activity of the grasshopper to the
empty, transparent phantom was less than thirty minutes. I placed the
unfortunate victim in a small, close box. Next morning he presented
nothing but a clean, glassy shell, now more glassy than before, empty
of every vestige of organic matter, while scattered about on the
bottom of the box lay fifteen dark red, egg-shaped chrysalides of the
escaped larvae. Two weeks later, upon opening the box, a swarm of flies
flew out. I was enabled to keep two of them. They were almost exactly
like the common house-fly to the ordinary observer, but belonged to a
distinct genus. At this writing, in the absence of my specimen, I
cannot give the name by which they are known in learned circles, but I
think I am safe in saying that they probably belong to the group
called _Tachina_, a family of parasitic flies which spend their early
lives in a similar questionable manner, to the probable discomfort of
potato-bugs, caterpillars, and other accommodating insect hosts.
I had seen similar flies emerging from my caterpillar boxes in my
early entomological days without suspecting their significance, and
any large collection of caterpillars in confinement is likely to
include a victim.