Saturday, November 18, 2017

Aphids on a Dock


On the MN training field trip to Henning Glade, Becky Swearingen and others found a prairie dock, Silphium terebinthinaceum, flower head covered with orange dots.  These were aphid larvae with an occasional adult, crawling all over the stem.  In the middle of the scramble there was a long flat area with a lot of "stuff" on it.  On closer inspection, this was the protective cover on the back of a debris-carrying lacewing larva.



We described these lacewings in a past blog but I took this one home with me for pictures.  When I opened the little insect box the next day, it was a scene of aphid carnage.  There were over 30 aphid carcasses scattered about, sucked dry by the lacewing larva.  It was interesting that during the feeding orgy within the confines of the little box it hadn't made any attempt to decorate its back with debris as it had the day before.


There are several possible explanations for this "naked" lacewing.  Some aphid colonies are protected by ants in a symbiotic relationship.  The ants get aphid honeydew and the aphids get protection from bullies like these lacewing larvae.  Thomas Eisner removed debris from some of their backs and showed that decorated lacewings could invade an aphid colony while naked ones were repelled.  It may also be that the day before it was just covered by crawling aphids.

Our Master Naturalist videographer Linda Bower has this clip showing a green lacewing larva grabbing an aphid (at :32 seconds) and then sucking away, earning its name as an aphid lion.

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