Caddisfly

lauriek · Post by **lauriek** » Sat Sep 19, 2009 11:24 am

Finally I've found what I think is a nice angle on a Caddisfly!

Stack of 38 images with OM 38/2.8 bellows lens. Stacked with Zerene stacker (Pmax)

Comments always appreciated!

rjlittlefield · Post by **rjlittlefield** » Sat Sep 19, 2009 11:41 am

Nice!

In addition to aesthetics, this image clearly shows the chewing mouthparts that are one of the distinctive differences between these things and moths.

I can't recall ever seeing a better illustration of that aspect.

--Rik

AndrewC · Post by **AndrewC** » Sat Sep 19, 2009 2:17 pm

Laurie / Rik: which are the mouth parts ? Just in between the two lower feelers ?

Andrew

rjlittlefield · Post by **rjlittlefield** » Sat Sep 19, 2009 3:35 pm

It's always hard to make sense of insect faces, and these things are worse than most.

At the top of the image are two antennae, with compound eyes below those. At the bottom of the image are two front legs, looking here rather like tree trunks. Everything in between are mouthparts of one sort or another.

The nominal arrangement for insects in general is that (quoting here from "How to Know the Insects", pages 31-32):

The mouthparts consist of an upper lip or labrum, a pair of mandibles, a pair of maxillae, sometimes a very short tonguelike hypopharynx, and a lower lip or labium. The mandibles may be stout, curved, and toothed for chewing (includes cutting, crushing, or grinding); long and needlelike for piercing and sucking; or otherwise modified. The maxillae also may be modified to pierce and suck in combination with the mandibles (e.g., mosquitoes, stink bugs, aphids) or they may be the only sucking organ (e.g. coiled proboscis of butterflies and moths). If the mandibles are used for chewing, the maxillae usually have short antennalike appendages (maxillary palpi) for touching and tasting materials. The labium may be somewhat flattened, bear short sensory palpi, and be used to guide food into the mouth opening.

Caddisfly mouthparts are illustrated at http://tolweb.org/Trichoptera, where they are described (somewhat inconsistently) as follows:

Also, unlike moths and butterflies, which typically have a coiled, tubelike proboscis for feeding, adult caddisflies lack well-developed mouthparts, including the absence of mandibles, but have a well-developed haustellum (synapomorphic for the order) formed from a fusion of the hypopharynx and labium, and used in some species to imbibe liquids.
...
Adult mouthparts are reduced, with mandibles essentially absent, but the maxillary and labial palps, and often the haustellum, are prominent.
...
Adult mandibles reduced, with loss of mandibular articulation

Adult prelabium joined with hypopharynx to form a unique "haustellum" which serves as a lapping/sponging organ

In retrospect, I should not have used the word "chewing". Caddisflies don't actually chew. Instead (again quoting from How to Know the Insects, pg.249),

(4) the maxillary and labial palpi are well developed; and (5) there is no coiled sucking tube for liquid uptake but instead a short, sucking tongue that is part of a rudimentary chewing mouthpart.

Getting back to the picture at hand... The two long "feelers" in the middle of the face are the maxillary palps, and the shorter feelers below them are the labial palps. I'm taking the two blocky things between the sets of palps to be those reduced mandibles, though I guess they may be parts of the maxillae. I don't see anything in this picture that I recognize as the haustellum.

I hasten to point out that I'm not personally expert in these critters, just interpreting the literature at hand. Perhaps one of our other members can make things right if I've scrambled the interpretation.

--Rik

lauriek · Post by **lauriek** » Sat Sep 19, 2009 4:34 pm

Thanks Rik, interesting stuff!

I don't know if this might help, it's a closer shot of the mouthparts, I didn't think it was quite such a nice shot but possibly shows more detail of the area in question...

Stack of 55 images with OM38/2.8, stacked with Zerene stacker Pmax.

I think we can just about make out the 'haustellum' in between the bases of the maxillary palps? There's a short tube which looks like it might have a hole in the end..

I thought this shot of a section of wing venation came out quite nicely as well;

Stack of 23 images with OM38/2.8, stacked with Zerene stacker Pmax.

rjlittlefield · Post by **rjlittlefield** » Sat Sep 19, 2009 4:45 pm

lauriek wrote:I think we can just about make out the 'haustellum' in between the bases of the maxillary palps? There's a short tube which looks like it might have a hole in the end.

Hmm, could be. Pretty indistinct still. In this view those blocky things look more like maxillae than mandibles also.

I agree that this is not nearly so pleasant a shot as the first one.

The section of wing is great!

--Rik

NikonUser · Post by **NikonUser** » Sat Sep 19, 2009 5:06 pm

rjlittlefield wrote: the chewing mouthparts that are one of the distinctive differences between these things and moths.
--Rik

Sorta, kind of, but not 100% accurate. There are some moths (Micropterigidae, Heterobathmiidae, Agathiphagidae) that have mandibles. Micropterigid moths use their mandibles to chew pollen grains for food.

rjlittlefield · Post by **rjlittlefield** » Sat Sep 19, 2009 5:17 pm

NikonUser wrote:Sorta, kind of, but not 100% accurate. There are some moths (Micropterigidae, Heterobathmiidae, Agathiphagidae) that have mandibles. Micropterigid moths use their mandibles to chew pollen grains for food.

Excellent -- thanks for the correction! I have never run into these groups.

I notice that Wikipedia describes Agathiphaga as "This caddis fly-like lineage of primitive "Kauri moths" was first reported by Lionel Jack Dumbleton in 1952, as a new genus of Micropterigidae."

Are these things considered to be phylogenetically close to caddis flies, or is this just a case of parallel evolution?

--Rik

NikonUser · Post by **NikonUser** » Sat Sep 19, 2009 5:50 pm

Sorry Laurie for getting away from your nice images; but to answer Rik's question.

I have always thought that Trichoptera (Caddisflies) and Lepidoptera (Butterflies and Moths) are phylogenetically close. Arnett (2000) "American Insects" states: [caddisfly]wings are covered with fine, short setae instead of the scales that typify their relatives, the Lepidoptera. Otherwise, they resemble certain moths in many details and are believed to be part of the same evolutionary branch as the Lepidoptera."
In one species of micropterigid moths the eggs are covered with gelatinous material, which swells when in contact with water, and presumably functions in the retention of water. This material, which may occur in the eggs of all species, resembles a similar layer in the eggs of many Trichoptera (Scoble 1995 "The Lepidoptera")

lauriek · Post by **lauriek** » Sat Sep 19, 2009 6:11 pm

NU No worries, I find this stuff fascinating!

One more attempt to show what I think might be the haustellum.

This is a 100% crop from the second image in this thread with some further levels adjustments.

rjlittlefield · Post by **rjlittlefield** » Sat Sep 19, 2009 6:37 pm

NikonUser wrote:...to answer Rik's question.

I have always thought that Trichoptera (Caddisflies) and Lepidoptera (Butterflies and Moths) are phylogenetically close.

Sorry, I didn't make my question clear enough. I'm aware that Trichoptera and Lepidoptera are close. The question was really whether the micropterigids are closer than other lepidoptera, or whether their more similar appearance is suggestive but misleading.

Laurie, that blowup is excellent quality for 100% pixels, but I still have no idea whether it's showing the haustellum or not.

There's an interesting side issue popping up here. You're now facing the problem of trying to get a good photograph of a specific piece of anatomy. In my experience, that turns out to be surprisingly more difficult than getting a good photograph of something that's visually interesting to start with. I'll be really interested to see the results, but I thought I should warn you that it's likely to be a frustrating process!

--Rik