We Have to go Deeper

A mass of yellow cocoons attached to the end of a twig.

Hi!  It’s been a few weeks, hasn’t it?  I have all these pictures and draft posts but no time to finish any of them because I am trying to get my analyses done for the ecology conference this August.  I am tragically productive.

Here are some cocoons I found up at the Oklahoma biostation back in spring.  Cocoons are awesome because they are basically insects you can rear without actually doing any work.  I stuck these guys in a jar for a week or two to see what would emerge.  What I got was tons of tiny black and brown wasps.  I took some pictures under a scope and threw them up on BugGuide where I they were quickly ID’ed by the excellent Bob Carlson.  BugGuide is awesome, because it is basically network of experts you can access without actually doing any work.

A female braconid wasp (Cotesia), emerged from the cocoons.

The black wasps turned out to be members of the genus Cotesia, in the family Braconidae.  These are parasitoid wasps which lay their eggs on (or in) caterpillar hosts.  The larvae develop inside the caterpillars Alien-style, slowly eating them alive, before eventually emerging to pupate and seek out new hosts.

A female ichneumonid wasp (Mesochorus) emerged from the cocoons.

The brown wasps turned out to be a species of Mesochorus which are hyperparasitoids of the original black wasps.  These are parasitoids of parasitoids which lay their eggs in the egg or early instar larvae of the Cotesia parasitoid wasp as it develops in the caterpillar host.  (Read that sentence back to yourself until it makes sense.)  If this arrangement seems unnecessarily complex to you, just realize that hyper-hyperparasitoids also exist.  Every “hyper” kicks it down another level.  It’s basically the plot of “Inception” but with innards-devouring bugs instead of dreams.  (“Insection“?)

Green Rooms and Gall Wasps

Eucalyptus leaf galls formed by gall wasps.

This is a green bug for St. Patrick’s day.  (I’m reaching; I know.  Happy Birthday, Eric!)

I’ve talked a bit about gall-forming insects in the past, but I think it bears repeating how extremely cool this adaptation is.  Galls are created by parasites (fungi, bacteria, mites, wasps, aphids, flies, midges, psyllids, etc.)  that use chemicals to co-opt the physiology of their host and cause the plant to grow abnormal structures that make a comfy little home for the parasite in question.  Opening up these particular leaf galls revealed tiny wasp pupae, developing in the safety and luxury of their own private green room.  Chemical warfare at it’s most refined.

Tiny gall wasp pupae inside a leaf gall.

P.S.  Does anyone know if any wasps outside Cynipidae form galls?  That’s the only family I’m familiar with.

The Standard Bearer – Ensign Wasp

An ensign wasp (Evaniidae) perched on a wall.

Due to their long legs and antennae, an ensign wasp on a wall may resemble a spider from a distance, and like spiders, they ought to be welcome guests in a home.  These little wasps are unable to sting and harmless to humans, but they are deadly to roaches.  Like many other small wasps, ensign wasps are parasitoids:  the female ensign wasp lays her eggs only in the egg cases of cockroaches, where the larvae hatch and quickly devour the cockroach eggs.

Ensign wasps (also called hatchet wasps) are members of the family Evaniidae, and take their common name from the distinctive shape of their gaster (rear end).  It is flattened laterally, and attached high like a flag.  Much like a banner waver, they will twitch their gaster rapidly up and down when disturbed.  The species I find around here is also notable for the attractive blue eyes that can be seen under a hand lens.  They main body is perhaps 1cm long, with the legs and antennae nearly doubling the size.  I found the wasp pictured above hanging around in the hallways of our building on campus, defending us from roaches.

Aliens

Parasitoid wasps parasitize an insect egg case.

Found these tiny wasps parasitizing a mantis egg case or ootheca in Argentina.  You can see the tiny wasps rearing up and inserting their long ovipositors.  In higher members of the order Hymenoptera, the female ovipositor is modified into the sting (only female bees, wasps, and ants can sting.)

‘Parasitoids’ are distinguished from ‘parasites’ in several ways.  A parasitoid insect lays one or multiple young on or into a single host organism–often a juvenile or egg.  The young develop inside the host, which may live on for some time, but almost always ultimately succumbs to the creature devouring it from the inside out.  Anyone who has watched the movie Aliens may find this sequence of events familiar.  Parasitoids thus are not true parasites as they kill their host, but not quite predators, in that they consume only one prey item during the course of their lifespan.

Ambushed Wasp – The Ambush Bug

An ambush bug preys on an unwary wasp.

Exploring an Argentinean roadside I spotted what I thought was a dead wasp on a flower.   Wondering how this wasp had come to perish so abruptly in her nectar gathering work, I looked closer.  I actually poked at her several times before I noticed the second occupant of the flower—an ambush bug enjoying a tasty wasp meal!

Ambush bugs are a subfamily of Assassin bugs, family Reduviidae.  Ambush bugs are “sit-and-wait” predators.  These highly cryptic (camouflaged) insects frequently lurk around flowers, where they pick off unwary visitors.  They have mantis-like raptorial forelegs to snatch their prey from a safe distance.   Like other true bugs (order Hemiptera, suborder Heteroptera) ambush bugs have a segmented tube-like ‘beak’ for feeding.  Ambush bugs insert this beak into a weak spot in their prey’s hard exoskeleton and suck out the fluids.