Saturday, May 12, 2007

Three insect mysteries from Spain

A disabled tarantula. It was a hot dry afternoon in late September. I had stopped the van where a narrow road crossed a slope of limestone scree at a high point on a remote road to the north-west of Guadalupe between Canamero to Navazuelas. We were above the tree line and whatever could grow there was not much more than knee-high. My companions for the day, very much in love, if temporarily, had wandered off to hold hands and converse, whilst a sudden movement close to my foot caught my eye and I looked down to focus on a small brown tarantula, maybe two inches long, that was running for its life, making lots of rapid loops and sidesteps, pursued on foot by a tiny black wasp. The strange thing was that the tarantula had only five legs, having lost two on one side and one on the other. I knew that there are parasitic wasps who will lay their eggs in a living spider & so my hopes were for the spider to escape, which he suddenly did by leaping upwards into a small clump of shrubbery, perhaps eight or nine inches off the ground, and hanging there by his two front legs in perfect stillness. The wasp was completely duped and ran around in angry circles for about a minute before wandering off in search of new prey. Why didn’t she know ? I called my companions over to see my new friend, but after a quick glimpse of him they instinctively felt they’d be safer back in the van, and so we drove on.

Processional caterpillars. In La Vera, on the southern slopes of the Sierra de Gredos, in March, whilst the weather is still quite cold, the hairy processional caterpillars ( thaumatopoca pityocampa ) let themselves down on threads of silk from the canopies of the pine trees to the forest floor. Never touch them or even disturb them without enormous care because their hairs provoke an intense allergic reaction. However, you can watch them gather and form their procession, each gripping the tail of the one in front, and marching off purposefully across the forest floor, the ones we saw numbered about seventy in the line. If you can find a long twig, place it gently under the belly of a caterpillar in the middle of the line and lift him gently until he releases his grip on the one in front. Immediately, I mean instantly, all the caterpillars in front will halt and they will wait until he rejoins the line. How do they know ?

part of the answer ...
http://web.cortland.edu/fitzgerald/PineProcessionary.html

Ants and peonies. I went in to a forest of small ancient evergreen oak trees for a pee, about three thousand feet up in the mountains. maybe forty miles north by north-east of Malaga, beyond the village of Alfarnate. It was about midday in March, but the sun was hidden and the weather was very cool. The forest floor was carpeted with wild peonies, at that point in spring where the tight spherical bud had formed at the top of the stalk not long before the flower opens. Bending down to look closer, I realized that on top of almost every bud there stood a single ant, one of those big ones whose head is so much bigger that its body. As you know, ants are busy & industrious, yet every single ant on every bud stood perfectly still. Why ?

Contextual information ... not an explanation ...

http://www.amjbot.org/content/89/8/1260.full.pdf+html