January 09, 2011

Skin Primer, Part 1

Since Bed Bugs feed by inserting their beak into the skin, I thought a primer on skin would be good.


This diagram image from Kidshealth.org shows a cutting of skin.

My questions are:

  1. What does the skin emit that lets the bed bug know skin is near?
  2. How deeply does the bed bug beak have to penetrate to get blood?
  3. Can bed bugs bite through a layer of material?
  4. How thick would the material have to be before the bed bug cannot penetrate the skin?
What skin emits:

From cosmetic sites I found out that skin actually does not breathe, so it does not emit carbon dioxide or any other waste gasses per se. However the sweat glands release salt, water and toxins, and the oil gland releases oil. When we sweat, as in during a work out, ketones get released in the sweat, a by product of breaking down fat. What does get emitted is infrared radiation.

How deeply a bed bug has to penetrate to reach blood:

Here is an image of the bed bug's mouthpiece from bed-bug.org:


What we need is a measurement.

To quote directly mdconsult.com (Ferri: Ferri's Clinical Advisor 2011, 1st ed.)

A bedbug’s bite is a wound caused by the penetration of the bedbug mouthpiece into the skin as the insect feeds on blood from vessels or extravasated blood from the damaged surrounding tissue.
Do they need to hit a capillary or a vein? Does breaking the skin, the outer layer cause bleeding?

To find out more I had to get more technical. The mouthpeice is called a "haustellum"which is defined as
haus·tel·lum/hôˈsteləm/ Noun: The sucking organ or proboscis of an insect or crustacean. (wikipedia - Merriam-Webster The Free Dictionary)
In looking for information about how deeply a bed bug has to insert the haustellum to get blood I came across an interesting examination of a tic-like blood sucking insect called a Ked engorging a mouse ear.


Melophagus ovinus: Feeding mechanism on transilluminated mouse ear
W.A. Nelsona and Denis M. Petrunia1,
Veterinary-Medical Entomology Section, Research Station, Canada Department of Agriculture, Lethbridge, Alberta, Canada

Abstract

Melophagus ovinus (L.), the sheep ked, when fed on a mouse ear, is a vessel feeder (solenophage). The haustellum of the ked penetrated the skin through the stratum corneum by rapid eversion of the prestomal teeth reinforced by pressure on the haustellum. It probed the subepidermal tissue with a reciprocating motion, accompanied by continuous activity of the prestomal teeth. When the labella contacted a venule of 30–100 μ, they immediately penetrated it, the prestomal teeth everted and anchored the labella to the vessel wall. Sucking of blood followed immediately and engorgement was complete within 5–10 minutes. Bursts of saliva were seen entering the vessel four or five times during engorgement. Sheep skin biopsy material containing the haustellum indicated that the ked fed from venules near the level of the apocrine glands and bases of wool follicles. Previous work is discussed in relation to these results.

Prestomal teeth. Labella. Bursts of saliva. This is what is happening folks!

I learned from cirrusimage.com/bedbug that
"[Bed Bug] mouthparts are modified for piercing and sucking.....Bed bugs grasp human skin with their forelegs, pierce the skin, and inject anticoagulant and anesthetic-containing saliva." 
which pretty well describes the above quote about the ked. The Cimex family (bed bugs) are also solenophages.

The stratum corneum (n. , pl. , strata cornea) is the horny outer layer of the epidermis, consisting mainly of dead or peeling cells, as per answers.com. I gather that the mouthpiece only needs to penetrate the outer dead skin layer, which, according to en.academic.ru/dic.nsf/enwiki/437704 is between .01 and .04 mm depending on the "grip requirements" (e.g. the palm or sole of the feet, it is thicker.) They provide this image of skin layers:



I have never felt bitten on the sole of my feet or on my palm so by this I see they prefer the thinner layer areas on the body.

Can Bed Bugs bite through a layer of material?:

Yes, they can.

How thick does it have to be so that the mouthpiece does not reach the skin?


I do not know yet, however in one experiment I have attempted to do with trapped bed bugs in a bottle is to cover the bottle opening with material and press this up against my skin and see how long it takes for the bed bugs to realize there is skin under there and to see if they take interest and try to bite.

This is how I got onto this line of questioning which is far from answered.

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