Tuesday, July 01, 2025

Heart-shaped wheel

 At the beaver pond today, the bluets were busy:

Boreal bluet, on hardhack leaf.

Mating pair, the male above, the female below. And her shadow.

With the damselfly clan, which includes the bluets, the female takes an active part in the mating game. (As opposed, for example, to spiders, where the female repels the male, and may eat him.) It's a four-step process; he prepares himself, transferring sperm from the back end of his abdomen to a pocket at the front; she grows a batch of eggs. Then he goes in search of a female, and grabs her neck with specialized claspers at the tail end of his abdomen. She, if she so chooses, then folds herself in half, to attach her tail end to the prepared sperm pocket, fertilizing her eggs.

They can fly around in this position (they call it the mating wheel); I saw two flying couples this afternoon.

When she's ready to lay her eggs, the male accompanies her, still holding her neck, as she visits the underwater plants where her babies will grow. She may need his protection; there's always the risk that she may get trapped underwater and drown before the eggs are all in safe places.

At the pond, these little blue arrows dart around, rarely stopping, always in a hurry. It's a hectic time of life for them, this being an adult: they've got a lot of egg-laying to do, and only a few weeks to do it in.

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En la laguna de los castores hoy, las libélulas estaban muy ocupadas:

  1. Azulilla de estanque boreal, Enallagama boreale, en una hoja de Spiraea douglasii.
  2. Una pareja, el macho arriba, la hembra (y su sombra) abajo.

Entre los caballitos del diablo, incluyendo a los del género Enallagma, la hembra toma parte activa en el proceso de apareamiento. (En oposición, por ejemplo, con las arañas, donde la hembra rechaza al macho o hasta lo come.) Es un proceso con cuatro etapas: (1) el macho se prepara, transferiendo esperma desde el extremo posterior de su abdomen hacia un órgano cerca del céfalotorax; la hembra produce un grupo de huevos. (2) Luego el sale en busca de una hembra, y la sujeta por la nuca con unos apéndices al propósito al final del abdomen. Entonces (3), ella, si le parece bien, se pliega y adhiere su extremo posterior al órgano copulador del macho, y así se fecundan sus huevos.

Pueden volar en esta postura; lo llaman el vuelo nupcial. Esta tarde vi dos parejas en el aire.

(4) Cuando la hembra va en busca de plantas subacuáticas donde pondrá los huevos, el macho la acompaña, deteniéndola todavía por la nuca, protegiéndola, pues siempre está en peligro de ahogarse en este momento.

En la laguna, estas flechitas azules se agitan, casi sin parar, volando a toda velocidad. Es una temporada de actividad frenética, esta etapa de vida adulta; tienen que implantar yoda la próxima generación y muy poco tiempo les queda de vida.

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