Wednesday, July 11, 2012

Net-winged Insects and the Strategies of their Predatory Offspring

There is great variety of species in the order Neuroptera, the net-winged insects, but they all have in common thin lacy wings, with forewings and hindwings of similar in size and shape, and biting chewing mouth-parts. Many species show some superficial similarity to Dragonflies, but they rest with their wings folded roof-like over their bodies. Their predacious larvae are terrestrial, except in Sisyridae. It's the larvae that show the most amazing strategies, from ambush in pits to chemical warfare. Neuroptera larvae pupate, often in a silky cocoon, and undergo a complete metamorphosis before hatching as winged adults.

Life cycle of a Common Antlion

Antlions are known to most people as the devious creatures that dig funnel-shaped pits in loose sand and not only sit in the bottom waiting for an unsuspecting ant that may fall in, but even throwing sand at their victims to make them loose their footing. I found them very difficult to photograph so I'm showing here an old illustration from Brehm's Thierleben (1895). The artist cheated: the larva on the left should be burried so only the pincer-shaped mandibles stick out of the sand. But I like the image because it shows the larva (left), the pupa (right) and the adult, winged antlion in the middle.
In North America only the antlions of the genus Myrmeleon dig those ant trapping pits. The larva in my picture was walking around openly catching insects under our porch light at night.

Vella fallax
An adult antlion Vella fallax was resting close by, but I'm not sure that this over 2 inch long adult was related to the larva.
Glenurus luniger
The diversity of antlion species in the desert around us is very high, they seem to be well adjusted to sandy soil and dry conditions (and lots of ants). But to see the pretty Glenurus luniger I have to take a trip to the mountains. This one is from Peppersauce Canyon in the Catalina Mountains.

Owlfly larvae
In Molino Basin, also part of the Catalinas, I found something that looked at first like a grass with dark seeds but turned out to be a group of first instar larvae of an owlfly. These young ones typically remain in a group with the original egg clutch for several days before dropping to the ground below and going their own predatory ways.

'trophic' eggs (left) and fertile eggs of Ululodes sp. photo by Hannah Nendick-Mason
 In the genus Ululodes the female provides her offspring with a series of club-shaped infertile eggs fastened below the regular eggs. These trophic eggs  (repagula) serve as the larvae's first meal and may prevent them from eating each other.

Owlfly
Also at Molino, this big owlfly was clinging to its perch so tightly that I could move it to find better light for my photos. Smaller species often appear at the black light, so they all seem to be night-active. Again, I do not know whether this is the same species as the clutch of larvae above.

Larvae of Brown and Green Lacewings
Meanwhile, at home, a strange shape is climbing a dried-up Brittle Bush. From above only a bunch of ant-body parts and exoskeletons is visible. The side view reveals legs and fangs that give away a Brown Lacewing larva. Probably very similar in built to the Green Lacewing Larvae that lived on the Brittle Bush flowers in spring, just smarter with its camouflage.

Green Lacewing eggs

Green Lacewing

 Adult Golden-eyed Green Lacewings are day-active and common year round. They feed on Aphids and other small insects. Their eggs sway on long stalks, protected from predators that come crawling along on the plant surface which may include their own older siblings.

Lomamyia sp., Berothidae (Beaded Lacewings)

Adult Beaded Lacewings are nocturnal and come to lights around our house in the desert bajada. They lay stalked eggs on wood surfaces near termite nests. The larvae move in with and prey on the termites. They discharge a gas containing an allomone  from their anus (Johnson and Hagen, 1981) to immobilize their prey.The gas is potent enough to paralyze several termite larvae and even adults at a time, but reportedly it has no effect on other non-termite 'house guests'.



Climaciella brunnea (Wasp Mantidfly)

When black-lighting for insects in the mountains, I often encounter several species of Mantid Flies.
They look and behave very much like small Praying Mantids. They use their raptorial arms to grab moths and other small insects that are also attracted by the light. In Arizona, the impressive Wasp Mantidfly lives in the canyons of the sky islands. While other morphs of that same species show brown and yellow banding of typical wasp mimicry, ours seems to mimic the coloration of Polistes comanche, the most common paper wasp of those habitats. Their larvae live as parasitoids in spider nests.






3 comments:

  1. I love this post and photos. Many things I didn't know and some I did. It's great to be reminded how nature in balance offers a better solution than the conventional Science-based choices as to pest control. Folks should stand back and educate themselves as to the reasons for eliminating pesticides all together and understanding exactly how the natural world truly works and replicate that in their backyards and landscapes.

    BTW, on a side note my wife and I were in Silkeborg Dänemark and met a couple from Norway. He is an American who married a Norwegian named --> "Margarethe"

    However he has trouble with the spelling and pronounciation so he calls his wife --> "Maggie"

    I'll always refer to you as Margarethe, don't worry.

    Thanks again for this interesting post.


    Kevin


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  2. Fascinating stuff. The owlfly larvae are amazing! And the wasp mantidly is yet another interesting example of mimicry (too bad I don't teach the concept of mimicry much anymore).

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  3. Wow! Incredible creatures!
    I had no idea you could find antlion larvae crawling around above the ground.
    And I never would have suspected that brown "stick of grass" to have a whole bunch of owlfly larvae clinging to it! Very cool photo.
    And the green lacewing larva covers itself in ant exoskeletons for camouflage???! That's insane!
    Thanks for amazing me!!!
    -Carol T.

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