Piercing/sucking

Actually, I was wrong about the CDC. They also have these cool SEM photos in their Public Health Image Library (search for old cimex l. on this page).

Like this one showing the fascicle of doom inside its sheath:

As described in Dickerson & Lavoipierre, the labium encloses the “needle-like stylets,” of which there are two pairs (mandibles are the outer pair and maxillae the inner pair) which together form a flexible “compact bundle” called a fascicle. The food canal (largish) and salivary canal (very small) are formed by the maxillae fitting together. The labium does not enter the skin; it bends to allow the fascicle to probe deeply into the skin. (To see photos of bed bugs feeding — and mating and being charming and all that — see this.)

All of this as it may be, once your mind latches on to an analogy, it’s hard to dislodge. Mine has been this one!

Not quite, but tempting.

Here is another view of the tip of the mouthparths:

What is that?

Like the spikes of a flail.

“The tip of the labium consists of 2 lobes bearing minute sensory papillae.” – Usinger, Monograph of Cimicidae, 1966.

But what are sensory papillae for?

Is the labium a suitable-skin-probing-site-sensing organ? And if so, what are the cues? Inquiring minds want to know… but can’t find out.

Anyway, while looking I found something that may interest you:

The bed-bug usually probes the tissues of the host repeatedly before settling down to feed, and it is most unusual for an insect successfully to locate a source of food immediately after the fascicle has entered the host’s skin. Sometimes probing is so prolonged that the insect becomes dissatisfied and completely withdraws the fascicle, changing its position on the surface of the skin and selecting a new site for probing.

Dissatisfaction? The mind reels.

Dickerson, G., Lavoipierre, M.M.J., 1959. Studies on the methods of feeding of blood-sucking arthropods. II. The method of feeding adopted by the bed-bug (Cimex lectularius) when obtaining a blood-meal from the mammalian host. Ann. Trop. Med. Parasitol. 53, 347–357.

This is their drawing of the stages of probing:

Bonus Dickerson/Lavoipierre:

Whilst probing, the fascicle often pierces, cuts across, and sometimes enters, minute capillaries and larger vessels, without ceasing its restless movement. This active probing results in the formation of small and large haemorrhages in the tissues, but we have seldom observed the bug to feed upon them. The fascicle continues its active movements in the tissues until it encounters and enters a vessel of suitable calibre, from which the blood-meal is then taken up.

What constitutes a “vessel of suitable calibre” is not elaborated upon except that they thought bed bugs ignored both very small capillaries and large blood vessels.

When engorgement is complete, the bug withdraws its fascicle, the blood pours out of the lacerated vessel, and a withdrawal haemorrhage is produced. If the fascicle has penetrated deeply into the tissues of the host the insect may have some difficulty in withdrawing it, owing to the small backwardly directed teeth on the tips of the mandibles, which fix them firmly in the tissue.

Blood and lacerated vessels. And we haven’t yet considered the saliva.

These pages may be of related interest:

1. Scenes from the battlefield: “NYC has an epidemic of them”
2. The lemonade file: “like giant pieces of beef jerky”
3. Permanent prophylactic measures, city of plastic bags
4. A mattress van of sorrows
5. The extravagant optimism of the DDT era