Tag Archives: insects

anything about insects

Oak Galls

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oak apple gall found fall 2012

A crisp brown ball, light and almost hollow, rests on the ground like squirrel’s toy ball.  The papery outside holds a light pithy center. Two small holes breech the dome like the secret holes in the ends of eggs blown for Russian decorating.

“Is this a puff ball?” a student asks, seeing one later on my desk. No, it isn’t . It is an oak apple gall, the home of the oak apple gall wasp (Amphibolips confluenta). This particular wasp was laid in the tissue of an oak leaf by  tiny mother wasp, who injected an egg  that triggered the oak leaf tissue to grow into this small home.  The larva developed there, and as I can see by the holes in the gall, has escaped.

For the most part these galls  don’t hurt the trees, and they make for an interesting food web. They also give us a little bit of history.  Oak galls are  famous as a source of gallotannic acid, once fermented and mixed with iron to form a dark ink (iron gall ink), the standard writing ink of Europe for seven centuries.

Galls are quite common on plants. These outgrowths or overdevelopments of tissue often take characteristic forms depending on the type of organisms that triggers them and the plant they are on. Usually they provide a home for an insect or mite, although sometimes they are more like a tumor, caused by   bacteria or a virus. Cedar apple galls,  orange fleshy aliens attached to cedar trees- reminiscent of some horror films, are caused by a fungus.

One gall you might be familiar with is the goldenrod stem gall. This hard swelling in the stem of a goldenrod is full of a dense whitish tissue. Cut open it will reveal a wriggling fly larvae (Eurosta solidaginis). Empty, it will look like a hard lump in a goldenrod. While it is developing, the larva eats the stem from the inside. Its saliva causes the plant tissue to grow abnormally. The larva spends almost a year inside the stem, growing, pupating and finally emerging as an adult who will live only two weeks and won’t eat.  When they are in the gall, larvae may be eaten themselves- by birds like chickadees. Can you imagine that the chipper, “Chicka dee dee” really means, “yum! I found a fly maggot in this hard abnormal growth” ? Two tiny species of wasps prey only on goldenrod gall flies- by parasitizing them.

Oh, but goldenrods are not the helpless victims you might imagine. Some plants produce a reaction called “hypersensitive necrosis” in order to protect themselves when they are infected or parasitized. This is quite common with bacterial infections but can also happen with insects and other invaders. The plants essentially sacrifice some cells by killing them, and wall off a pathogen or in this case, a larva, so that it dies – a grisly death that can only be imagined by readers of Poe.

Galls can look like skin tags,  warts,  lumps, hedgehogs, appalling tumors, artichokes, caterpillars, wooly marbles, corn kernals, small lumps, and every imaginable bump and mound.  The ones I see most often – the oak leaf galls and the golderod stem gall, hold the creepy hope of new life, and the promise of plant survival by a continual fight against invasion.

For more on galls:

http://www.maine.gov/agriculture/pesticides/gotpests/diseases/factsheets/galls-cornell.pdf

For more on goldenrod gall fly:

http://www.fcps.edu/islandcreekes/ecology/goldenrod_gall_fly.htm

more on the hypersensitive response: http://www.icb.ufmg.br/labs/leeb/publicacoes/1990.Fernandes.pd

iron gall ink

http://en.wikipedia.org/wiki/Iron_gall_ink

Winter Moth Returns

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I originally wrote this piece in the fall of 2008, when there were enormous numbers of moths out right around Thanksgiving. I sent it around to colleagues at school where it was well received. Originally it referred to a couple of people by name. Here I just use initials. Tonight (Nov 21, 2012) moths are out in force in my yard, in the headlights of my car.  Time to repost!

photo by F. Lamiot, 2006, from Wikipedia commons

Enquiring Minds have been asking…

Leaving west campus in the dark of early evening, I have been bombarded by clouds of fluttering moths at the glass entrance to the building. They lie in the wet of the sidewalk, bang against my face, tap on my hands as I flick them away. You have seen them too, I know, because I hear the tidbits of lunch room speculations, references to the movie “The Birds”.

Will they take over? Will Hitchcock’s legacy live on in some dreadful horror flick in which  staff and faculty are battered to death by moths? Moths in the eyes (Ta dum ta dum) the mouth (the horror!!)? -JM running screaming into the building, beating back the flurry of powdered wings , GC found frozen in terror, covered by moths, almost to his car at the chapel lot….

Possibly. I can’t really speak to that. But if you wondered, they are males of the winter moth(Operophtera brumata), a  European species introduced about a decade ago that has taken over the Thanksgiving and Advent periods in eastern Massachusetts for the past several years.  The larvae are those light green inchworms that so devastate your crabapple and oak trees in the spring, leaving only skeleton veins of those first juicy leaves. The house sparrows love them.

But only males?  Yup. The females are flightless. If you look closely at walls and doors, you will see what look like  mutant moths, just bodies with tiny wrinkled vestigal wings. They are supposed to be like that. They sit there and send out chemicals more powerful than the best Christmas present perfume, that call to the males, “come find me” and apparently it works, except for all the males lost trying to get to the lights through the glass doors at west campus, or feebly pulsing in the puddles that I pass.

Winter moths are similar to the native fall cankerworm. It comes out at the same time, and also has flightless females. But cankerworms don’t build up the huge numbers we have been seeing during this season weeks. So these are almost certainly the European winter moth.

So, if you have been wondering, there you have it. If you haven’t been wondering, get out and notice while they are still around! U Mass extension says we may be in for more winter moths than usual if the winter is mild.

More information is available through UMASS extension for those who really want to know…http://extension.umass.edu/landscape/news/warm-winter-2012-and-what-expect-winter-moth-massachusetts

Red Headed Pine Sawfly

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Several Weeks ago I saw these  hidden in, and eating, the needles of a Scotch pine. (I’m reasonably sure on the tree, if you know otherwise, say so)

 

 

Oct 12, 2012:

At first I thought there were only a few of the yellow-green spotted  larvae tucked into the pine needles. Each one has a sweet scent of pine, and they look like caterpillars.  However,  they are not , they are the Redheaded  pine sawfly (Neodiprion lecontei). Sawflies look like flies as adults and like caterpillars as larvae but they are neither flies nor moths and butterflies.  In fact they are in an order of insects more closely related to primitive wasps than anything else.  Unlike Wasps, they have a wide waist. Unlike true flies, adult  sawflies have two pairs of wings.

Why “sawfly”?  The females have a serrated ovipositor they use to saw a hole in a plant to lay eggs.  Most eat plants, and some, like this one, can kill a tree.

As I peered, I saw more and more. They reared up in unison, curving their backs and rearing their three pairs of legs, in the front. They, like caterpillars, cling with what look like extra legs- but they aren’t. Lacking joints, the extra stubs are called “pro-legs”. The rearing behavior is a defense mechanism.

Sawflies can kill a tree by eating all the needles if they do it a couple of years in a row. But these are unlikely to.  As I follow their progress ove rthe next week, they eventually eat about a sixth of the tree’s needles  and I knock them to the ground over a period of days-  calling it “Integrated Pest Management” each time.   Some I know will survive for next year.  Nice to see a new insect I has not noticed before, and to protect the little pine!