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Ixodes adult female? - Amblyomma

Ixodes adult female? - Amblyomma
San Francisco, San Francisco County, California, USA
June 6, 2012
Size: 3 mm
Given to me for ID - possibly an engorged adult female I. pacificus?

Images of this individual: tag all
Ixodes adult female? - Amblyomma Ixodes adult female? - Amblyomma

Moved from Dermacentor.

aftter further review...
I do not think this is Dermacentor. I think it is an Amblyomma nymph, but I am unaware of Amblyomma in CA. Could it be imported? Do you remember where the host traveled to (if human)?

Unfortunately -
this was found on or near a human, but I have no way to figure out a travel history or get any details at this point...

Agree Amblyomma
Looking at this again, I agree it's probably an Amblyomma nymph. I ran it through the Keirans and Durden key for Amblyomma nymphs and think it could be A. cayennense/imitator, with a huge grain of salt that some characters are absent or can't be seen, these ticks are found in TX at the maximum northern extent, and we don't know what it engorged on (reptile vs. mammal or bird).
Pro A. cayennese points:
Very common in Central America
No internal spurs on coxae II-IV
Shortish spur on coxa IV

Moved from Hard Ticks.

Not Ixodes
This is an engorged nymph, not genus Ixodes due to presence of eyes and Y-shaped groove posterior to the anus. I would guess Dermacentor. On a side note, the white lines visible on the back are malpighian tubules seen through the stretched cuticle, leading into the hindgut sac on the ventral side. The white color is from guanine crystals, ticks' primary waste product.

Thanks, Jon!
Great comments - very helpful. May I ask how you are ageing it as a nymph? Feel free to email me offline - I get asked to help ID bugs at work sometimes and I'm dismayed that I missed this one. A little knowledge can be a dangerous thing, I suppose...

Nymphal characters
The initial hint that this is not an adult is the size. 3 mm is awfully small for an engorged adult Ixodes, particularly I. pacificus which you would expect to be pushing 1 cm.

The clincher for identifying adult vs. nymphal ticks is the presence of the genital apperture, a U- or V- shaped opening on the ventral side between the legs. This is present in adult ticks, but absent in nymphs.


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