Of cornicles and lace

Beasties Project, continued. A two-fer, today.

Aphids:

Red and green aphids.

I sent these in to BugGuide, with a question: Are the green aphids immatures, or a different species of aphids? The answer: probably nymphs, immature stages on the way to becoming adults. And the adults here are possibly potato aphids, Macrosiphum euphorbiae. They feed on a huge variety of plants; these were on my lemon balm, but may have been feeding before on the scarlet runner beans or the sweet peas, or any of the weeds that persist in infesting my patch.

Adult and youngster.

Oh, the rabbit holes I fall down! I see Macrosiphum euphorbiae, and here we go. Whee! Macrosiphum translates as Big Siphon, referring to those two tubes on the sides of the end of the abdomen. Tubes, or siphons; but BugGuide calls them siphunculi, and looking that up for a definition, I got cornicles. As in, all aphids have cornicles; that is how you can distinguish them from nymphs of some other insects. The potato aphids have very long cornicles.

Got it. So the cornicles are important, but what do they do? I had heard that they excrete sweet honeydew, and that is why the ants farm them, but it's always good to double check. And no, that was what was thought before, but more recent studies show a different purpose.

Smaller aphid, on yarrow. Same day, probably an early stage. The cornicles are barely visible.

It’s now understood that this second liquid actually contains lipids, hemolymph and a substance called an alarm pheromone. (TheBugChicks)

The pheromone in question, E-β-farnesene, warns other aphids that a predator is nearby.

An aphid only produces E-β-farnesene after it’s been attacked.  Once that pheromone is released, any aphid within detection distance will stop feeding and walk or fall of the leaf it’s on.  In species with long cornicles, (like the potato aphid) the aphids will flex their abdomens and smear the pheromone onto the predator in the moments before death.  This action ensures that wherever the predator goes on the plant, the other aphids know before it even arrives!  It’s totally sneaky.  This behavior allows the other aphids in the cluster more time to escape predation. (TheBugChicks)

And here's a predator: a lacewing.

Brown lacewing, subfamily Hemerobiinae 

What big eyes you have, Lacey!

The lacewings, both the greens (of which some are brown) and the browns (which may turn green with age) are predators. And both larvae and adults indulge. Their favourite food is aphids.

They hunt from dusk to dawn, and on cool days. This one turned up at my desk at 9 in the morning. After a successful night among my flowers, I hope.

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Seguimos con el Proyecto Bichitos. Dos criaturas hoy.

Los áfidos. También se les llama pulgones.

Fotos: #1, 2. Áfidos, rojos y verdes, adultos e inmaduros.

Envié estas fotos a BugGuide, con la pregunta: ¿Los áfidos verdes, son inmaduros, o de otra especie distinta? La respuesta: probablemente son ninfas, áfidos inmaduros. Y estos adultos posiblemente sean áfidos de las papas, Macrosiphun euphorbiae. Se alimentan de una gran variedad de plantas; estos estaban en las hojas de toronjil, pero bien pueden haber estado antes en mis plantas de frijol escarlata, o en los guisantes de olor o en cualquiera de las hierbas malas que llegan a invadir mi jardín.

¡Qué fácil se me hace desviarme! Veo el nombre científico, Macrosiphum, y ya perdí el camino. Macrosiphum se traduce como Sifón Grande, y se refiere a esos dos tubos que salen a ambos lados del extremo del abdomen del áfido. Son tubitos, pero BugGuide los llama siphunculi. Buscando la definición de esa palabra, me llevó a los cornículos. Todos los áfidos tienen cornículos; de esta manera se puede distinguirlos de las ninfas de algunos otros insectos. Los áfidos de las papas tienen cornículos muy largos.

Todo muy claro. Pero, ¿de qué sirven los cornículos? Había oido antes que secretan el melazo tan dulce, la razón por la cual las hormigas los cultivan, pero siempre vale la pena volver a investigar. Y resulta que eso es lo que pensaban antes, pero estudios más recientes descubren un propósito distinto.

Foto #3: Un pulgón más chico, probablemente más joven. En aquilea sp..

Ahora se entiende que este segundo líquido contiene lípidos, hemolinfa, y una sustancia llamada una feromona de alarma. (TheBugChicks)

La feromona referida, E-β-farnesene, sirve de advertencia para otros áfido que un predador se encuentra cerca del grupo.

Un áfido solamente produce E-β-farnesene después de que ha sido atacado.  Una vez producida esa feromona, cualquier áfido dentro de una distancia que permite detectarla dejará de comer y caminará o se dejará caer de la hoja donde se encuentra. En especies con córniculos largos (como el áfido de las papas), los áfidos doblarán sus abdómenes y untarán el predador con la feromona en los momentos antes de morir. Esto asegura que dondequiera que vaya el predador sobre la planta, los otros áfidos lo sabrán ¡antes de que llegue! Completamente tramposo. Esta forma de actuar les da más tiempo para escapar al predador a los otros áfidos. (TheBugChicks)

Y aquí hay uno de esos predadores: una crisopa parda.

Fotos #4, 5: Crisopa parda, con sus alas como encaje y sus ojos grandes.

Las crisopas, tanto las verdes (de las cuales algunas son pardas) y las pardas (que pueden volverse verde al madurar) son todas predadoras. Y tanto las larvas como los adultos así se alimentan. Su comida favorita es un áfido.

Cazan de noche, desde el crepúsculo hasta el amanecer, y también en dias frescas. Esta llegó a mi escritorio a las 9 de la mañana. Después de una noche exitosa entre mis flores, espero.

Aphid in Sheep's Clothing

I will never grow up. I am still asking small-child questions: "What is this?" "What does it do?" "Why?"

The green bugs Laurie brought me the other day have been keeping me busy. Google was little help, this time; I had nothing to go on, other than "green bug, alder, cottonwood". I posted my photos, such as they were, on Bug Guide; the next morning, a commenter said they looked like "woolly aphids". Back to Google, to research woolly aphids on alder.
First, I discovered that woolly aphids produce their own "blanket"; it is not cottonwood fiber, even though it looks similar, and is also coating leaves in the vicinity. Instead, it is a waxy substance that they exude from the anus, as other aphids exude honeydew.

I compared a cottonwood twig, with seeds and fiber, with the fiber from the bugs. The cottonwood was not quite as white, silkier to the touch and more "feathery". Fiber from the suspected aphids was sticky; cottonwood fiber was sticky only when it had already come into contact with the leaves where the bugs were. So that checked out.

But then I ran into problems. The woolly alder aphid is common in BC, is covered with a white, sticky fibrous blanket, migrates from maple to alder in early summer, and eventually covers the leaves with a sticky nectar which leads to the growth of a blackish mold. Check, check, check, check and check. Except that all the photos of woolly alder aphids without the coating were nothing like mine. Wrong colour, wrong eyes, wrong shape.
A close-up of my bug, shorn of its "wool". Note the little wings or wing covers; he beat those winglets, but never managed to fly with them. Also note the absense of visible mouth parts or pincers. And the "goggles"; black circles around the eyes, as though written on with a felt pen. The tail is black, but in two sections, with the rear-ward one being slightly greyer. You can see where the wool is produced; a small bit still sticks there. (Ignore that red fiber: it's a piece of my carpet.)

I looked at hundreds of photos of woolly aphids, of all sorts; none of the denuded bugs were anything like mine.

Could something else mimic these? Something that, under the disguising blanket, turn out to be another beast? A predator? A "wolf in sheep's clothing," in miniature?

In the New Westminster Library, I searched the indexes of insect books for "woolly aphid". Mostly, it wasn't there, or referred to one or two lines of text. But there was a new (to the library; it's from 2003) book: For Love of Insects, by Thomas Eisner. And it has 20 pages on woolly aphids, a mimic, and its interactions with the aphids and the ants that "farm" them.

The green lacewing larvae prey on woolly aphids. Some of these are known as "trash bugs"; they purposefully coat themselves with bits of debris, including food leftovers. Eisner discovered some of these that took the waxy fibers from the woolly aphids, and covered themselves with them, until they could pass for a large aphid themselves.

He pulled the covering off some of these, the same way I had with my bugs, and watched. They immediately set about covering themselves again, grabbing pieces and twisting around to place them on their spiked backs until they were completely disguised again. (I went back and looked at the bugs I had stripped the day before; they were also back to normal, sheep ready for the shearing.)

Ants are well known for their talents as aphid farmers. They will stand guard over their herd of aphids, protecting them from wasps and other invaders, including humans, and "milking" the aphids for honeydew by stroking them with their antennae. The woolly aphids also produce this honeydew, along with the wool, and are shepherded by ants for this purpose.

The green lacewing larvae escape the notice of the ants by stealing the waxy fibers from the aphids they will be preying on. Eisner and his staff stripped the larvae and placed them back in the colony of aphids; ants attacked them right away. Some they killed outright, others they carried away and threw off the branch. A few were eaten. But an ant that bit a larva coated with fiber got a mouthful, and retreated to clean himself off. After a few attempts, they ignored the larvae.

So: were my bugs lacewings? If so, it was odd that I hadn't seen any lacewing eggs anywhere; these are noticeable, because they lay them one at a time on top of a 1/2 inch stalk. To me, they would look at first glance like one variety of slime mold, which I keep a lookout for.

And none of the lacewing larvae looked anything like my bugs, either.

Besides, all the lacewing larvae that I could find, and all the descriptions, mention the large mouthparts , the "powerful jaws" "like ice tongs". My bugs have no visible mouthparts at all, no matter what position I prodded them into. And smooth bodies, with no spikes.

So, what are they? I still don't know. For now, I'm going with "woolly aphid". But not the woolly alder aphid, nor either of the two invasive woolly aphids here in BC, the woolly balsam aphid and the woolly hemlock aphid.

A "normal", non-woolly aphid, on another leaf from the same tree, for comparison purposes.