Width of the grass blade is 4.2 mm, blob takes up entire width
Apart from a spot of tar, I don't believe this can be confused with anything else in nature.
What is it ? (2nd image added 1vii09)
Moderators: rjlittlefield, ChrisR, Chris S., Pau
What is it ? (2nd image added 1vii09)
Found this today on a blade of grass growing in a roadside ditch.
Width of the grass blade is 4.2 mm, blob takes up entire width
Apart from a spot of tar, I don't believe this can be confused with anything else in nature.
Width of the grass blade is 4.2 mm, blob takes up entire width
Apart from a spot of tar, I don't believe this can be confused with anything else in nature.
Last edited by NikonUser on Wed Jul 01, 2009 5:38 am, edited 1 time in total.
NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.
Nikon camera, lenses and objectives
Olympus microscope and objectives
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.
Nikon camera, lenses and objectives
Olympus microscope and objectives
Yes Betty, correct. Almost certain to be a Hybomitra as we have few Tabanus here and they fly later in the year.
Apparently some tabanid masses are dark brown but all I have seen are always this shiny jet black. When laid they are white but very quickly tan to black.
The eggs are heavily parasitized by tiny hymenopterous parasitoids which oviposit in the individual tabanid eggs almost immediately after they are laid and before the cuticle has hardened. Image from a Kd slide below (Hybomitra lasiophthalma + parasitoid).
Aynia: yes all eggs are separate, laid one-at-a-time. Deer Flies tend to lay the eggs in one layer, Horse Flies lay them in tiers as here. There are probably 200 eggs here, not sure how the guy/gal in the dead center in the middle of the mass gets enough air.
Apparently some tabanid masses are dark brown but all I have seen are always this shiny jet black. When laid they are white but very quickly tan to black.
The eggs are heavily parasitized by tiny hymenopterous parasitoids which oviposit in the individual tabanid eggs almost immediately after they are laid and before the cuticle has hardened. Image from a Kd slide below (Hybomitra lasiophthalma + parasitoid).
Aynia: yes all eggs are separate, laid one-at-a-time. Deer Flies tend to lay the eggs in one layer, Horse Flies lay them in tiers as here. There are probably 200 eggs here, not sure how the guy/gal in the dead center in the middle of the mass gets enough air.
NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.
Nikon camera, lenses and objectives
Olympus microscope and objectives
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.
Nikon camera, lenses and objectives
Olympus microscope and objectives
-
rjlittlefield
- Site Admin
- Posts: 23606
- Joined: Tue Aug 01, 2006 8:34 am
- Location: Richland, Washington State, USA
- Contact:
Very nice! That last image is worthy of Life in the Undergrowth. 
I'm having trouble imagining how that little wasp and all its brothers and sisters manage to keep going.
It sounds like she has only a very short time to find and parasitize an egg mass. But the flies are large and fast and can cover a very large area, while the wasp is small and slow and must be confined to a much smaller area.
So how does this work? Do the flies lay eggs only in certain small areas, and the wasps hang out there waiting for them? Is there a big cloud of scent surrounding an ovipositing fly? Do the wasps find a fly at their convenience and hitch a ride until it's time to lay eggs? Do the wasps have other more tractable hosts to keep up the population? Or something else? Or is this still a mystery?
--Rik
I'm having trouble imagining how that little wasp and all its brothers and sisters manage to keep going.
It sounds like she has only a very short time to find and parasitize an egg mass. But the flies are large and fast and can cover a very large area, while the wasp is small and slow and must be confined to a much smaller area.
So how does this work? Do the flies lay eggs only in certain small areas, and the wasps hang out there waiting for them? Is there a big cloud of scent surrounding an ovipositing fly? Do the wasps find a fly at their convenience and hitch a ride until it's time to lay eggs? Do the wasps have other more tractable hosts to keep up the population? Or something else? Or is this still a mystery?
--Rik
Doug:
been a while since I was at school but the darkening process is probably due to 2 processes:
i) the deposition of melanin in the skin of the egg. A complex chemical process.
ii) the egg shell is initially soft and it gets hard due to the cross-linkages between protein molecules, this process also causes darkening of the skin.
Rik:
Don't know how, but tabanids are very common and oviposit on vegetation low down in very wet areas and usually over water. Thus the wasps have a relatively small area to search (of course there are always exceptions, some tabanids lay eggs on tree leaves in relatively dry forests!).
There are probably as many wasps as there are tabanids.
I suspect there must be some scent from ovipositing flies, I can't see how they could otherwise locate the egg mass so quickly. I doubt they are hitch hikers.
Alternate hosts is an interesting concept.
Horse fly lays eggs - wasps lays eggs - wasp hatches in a few weeks - maybe finds another egg mass - new wasps a few weeks later - but now it's mid-late Summer - no more tabanid eggs - how do you get through Winter?
A Manitoba study found that 98.9% of 93 eggs masses were parasitized
HERE
been a while since I was at school but the darkening process is probably due to 2 processes:
i) the deposition of melanin in the skin of the egg. A complex chemical process.
ii) the egg shell is initially soft and it gets hard due to the cross-linkages between protein molecules, this process also causes darkening of the skin.
Rik:
Don't know how, but tabanids are very common and oviposit on vegetation low down in very wet areas and usually over water. Thus the wasps have a relatively small area to search (of course there are always exceptions, some tabanids lay eggs on tree leaves in relatively dry forests!).
There are probably as many wasps as there are tabanids.
I suspect there must be some scent from ovipositing flies, I can't see how they could otherwise locate the egg mass so quickly. I doubt they are hitch hikers.
Alternate hosts is an interesting concept.
Horse fly lays eggs - wasps lays eggs - wasp hatches in a few weeks - maybe finds another egg mass - new wasps a few weeks later - but now it's mid-late Summer - no more tabanid eggs - how do you get through Winter?
A Manitoba study found that 98.9% of 93 eggs masses were parasitized
HERE
NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.
Nikon camera, lenses and objectives
Olympus microscope and objectives
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.
Nikon camera, lenses and objectives
Olympus microscope and objectives
-
rjlittlefield
- Site Admin
- Posts: 23606
- Joined: Tue Aug 01, 2006 8:34 am
- Location: Richland, Washington State, USA
- Contact:
Nice report. At first I wondered how the poor tabanids kept going. Then I read the details.
So while almost all of the egg masses in this one area were attacked, still about 41.7% of the eggs were not parasitized and did hatch. ( (1-.345)*(1-.363) = .417)We found that 98.9% of the 93 multi-layered egg masses of H. nitidifrons nuda were parasitized by two species of Telenomus, here designated as species A and B. A mean of 34.5% eggs within individual egg masses were attacked. In addition, 36.3% of all unparasitized eggs failed to hatch.
--Rik