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Wednesday, August 31, 2011

Tobacco Hornworm (Manduca sexta) and the Parasite Wasp (Cotesia spp.)

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The picture on the left is the tobacco hornworm (Manduca sexta) that infested my tomato plant.  The insect belong to Sphingidae family, commonly known as hawk moth.  The tobacco hornworms can be distinguished from the closely related tomato hornworms by their seven diagonal stripes versus eight v-shaped marking on the tomato hornworms.  The most striking feature of the hornworm is the thick pointing structure (or horn) located dorsally on the terminal abdominal segment.  On the back of the larvae, there are clusters of parasite wasp cocoons which has be infested the larvae and emerge from the skeleton.

This post, I am getting some close-up view of the tobacco hornworm and the parasite wasps under a stereo microscope.

Close-up of the tobacco hornworm

tobacco_hornworm_mandible
Mandible of the larvae (slightly out-of-focus are the thoracic legs)
tobacco_hornworm_ocelli
Ocelli
thoracic_legs_antenna
Thoracic legs
tobacco_hornworm_proleg2
The tip of the prolegs on abdomen.  Now, you know why it is so hard to remove the caterpillar from the tomato vine.  They are full of “claws”.
tobacco_hornword_spiracle
Spiracles
tobacco_hornworm_spiracle_large
Another view of the spiracle (with 4x objective rather than 2x)
tobacco_hornworm_parasite_lesion
The spiracles and the lesions caused by the parasite wasps
tobacco_hornworm_lesion2
tobacco_hornworm_terminal_segment
The terminal segment of the abdomen.  The end is full of spikes.  That’s how they stick to the vine when you are trying to pull them off the vine.
tobacco_hornworm_horn
The horn - “signature” of the tobacco hornworm.

The parasite Wasp

tobacco_hornworm_parasite_wasp_cocoon
Day3 (8/29/2011): The cocoons of the parasite wasp at the dorsal of the tobacco hornworm (this picture was taken about 48 hour after we collected the hornworm)
tobacco_hornworm_parasite_wasp_larvae2
Cut open the cocoon, there was a larvae inside
tobacco_hornworm_parasite_wasp_larvae
Continue to peel open the cocoon.  Here’s full view of the larvae.
tobacco_hornworm_parasite_wasp_cocoon1
Day 4 (8/30/2011): Just one day after I opened up the cocoon.  Apparently there was a big change inside of the larvae.  It’s already taking the shape of the wasp and with legs and pigmented eyes developed.
tobacco_hornworm_wasp_day3
Day 5 (8/31/2011): Start to show darker pigmentation
tobacco_hornworm_wasp_day4
Day 6 (9/1/2011): Even Darker pigmentation.  Still no movement
tobacco_hornworm_wasp_day7
Day7 (9/2/2011): The appendages and antennas are starting to extend out and show some movement.  Occasionally, it would tweet its legs or antenna.  Wings are more visible now.
cotesia_cocoon
The wasp starting out with cutting a ring close to the top of the cocoon.
cotesia_cocoon_initial_push
It did not cut all the way through.  It started to push when it the cut was about 90 percent of the circumference.
cotesia_cocoon_half_way_out
Continue to push.  First the antenna then the two front legs.
cotesia_cocoon_completely_came_off Finally, completely came out of the cocoon.

 

wasp_stichThe wasp that was removed from the cocoon did not survive.  Its wing did not extended out fully.  The picture on the left was another wasp that came out of cocoon on the same date. The pictures were combined using Microsoft image composite Editor since the antenna are very long and extended out of the field of view.

cotesia_top cotesia_bottom

 

Video recording of the parasite wasp come out of the cocoon

13 comments:

  1. O_0 omg! would love to see that in real life!

    ReplyDelete
  2. Awesome blog!!
    I never see this type of pics before.
    Thanks for the post.

    ReplyDelete
  3. Hi
    Really like the photos on your blog - do you have a page describing the equipment and software you use? I have a binocular microscope and struggle to find a good quality camera that will fit into the eyepiece tube - so my photos are nowhere the quality of yours.
    Cheers
    Nige
    info@thinked.com.au

    ReplyDelete
    Replies
    1. You can find the equipement in my toys page:
      http://practical-microscopy.blogspot.com/p/my-toys.html
      The camera was Canon EOS T1i, I purchased the camera adapter from Amazon. The diameter (22.5 mm) for the adapter is too small for my ample scientific SM-Plus stereo microscope (30.5 mm) so I added another adapter ring from my Tuscen reduction lens kit.

      Delete
  4. Hi,

    I'm also currently working on parasitoids larvae for my master research, and I need to take photos of the larvae for morphological descriptions. My problem is that the photos that I took were not as sharp and clear as yours since the larvae are small. I used Olympus camera with 2X -4 lens that attached to microscope. But all my photos were blur and the color were not same as the real one. Can you help me on this?

    ReplyDelete
    Replies
    1. Every camera is a little bit different. I am using Canon EOS T1i. I am not sure whether your camera support PC connection and the image can be view through software. It will be easier for you to focus. As for the color, try to use different color balance settings. For my canon, I am using video mode to take picture - it automatically selects the light source.

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  5. Well now a days lots of cameras to be use on how to capture like that images.. I think its called macro photography with the help of macro lens you'll gonna get a shots like that.. and as far as I know those worms are being cultured because their cocoons are being used to make silk fibers..

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  6. Thank you for this! I've had quite a battle with tobacco hornworms due to our unseasonable weather. I pulled at least one hundred of the pests off of my nine tomato plants. At first I was indiscriminate, but I noticed what looked like parasitical eggs on their backs. I learned about the brachonids (as we have other species that oviposite wood boring beatle larvae) it made sense to me that the tobacco hornworm could be susceptible to such a predator. What a great example of adaptation!

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  8. Thanks a lot for creating this blog!!
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