Can someone help me with the definitions of xanthic and melanic concerning wasp patterns.
I know it has something to do with the alterations of the patterns, some having more yellow and others more black, but I couldn't find a complete explanation for it.

Can someone help me?

Moved from Vespula.

to Vespula but thumbnail of this image placed on the Info page of both Eastern and Yellow-Haired

Even without being able to see the profile of tergite 7, I would say this is a large, extremely xanthic specimen of V. maculifrons. I have encountered specimens like this before. In my experience, V. flavopilosa males that are this xanthic do not have an enclosed area on T-1 (approaching a diamond); this area still maintains its "V" shape although the angle is lessened. Also, flavopilosa that is this xanthic rarely has the lateral black projections on T-2 still attached to the black anterior region.

V. maculifrons with this coloration are more common farther south such as in Florida but may be found in other parts of the species' range.

I agree that there is no chance of this being V. pensylvanica.

The key you are quoting is probably conceived for WORKERS only, because ALL vespula males DO have a yellow spot in front of their antennal scapus. Therefore, it's quite logical that "nothing fits" on the couplet nr. 7.
Ironically, some V. pensylvanica males indeed lack, or almost, the yellow ring around the compound eyes. But contrary to what you're writing, V. pensylvanica's abdominal pattern doesn't fit at all whith this one male, for at least three reasons:
- V. pensylvanica's black, diamond-shaped spot on the first tergite is MUCH MORE POINTED, forming an acute angle: here, this angle is quite superior to 90°. I agree that it could look a bit "narrow-necked" for a typical V. flavopilosa, but the reason for this is that this one male is relatively xanthic (hence the almost free spots on the second tergite).
- the same is true for the second tergite: the median black angle is very acute too, and moreover ALMOST REACHES THE APICAL MARGIN, in any worker or male V. pensylvanica specimen. Quite obviously, it is not the case here.
- on the same sclerite, the lateral spots are clearly DIVERGING here, which perfectly fits with the sketch of a typical worker specimen's abdominal pattern of V. flavopilosa in Akre et al (1981). On the contrary, these lateral lobes in any V. pensylvanica male or worker specimen ALWAYS start from the basal margin, not from the median lobe, and are STRICTLY PARALLEL with the axis of the abdomen, sometimes even slightly converging.

So this male can only be a yellow-haired Yellowjacket, V. vulgaris being eliminated as I have previously explained (I agree that the old common name "hybrid" is not so good, for this species is probably not an hybrid at all, but rather results from an earlier colonization of North-America by the ancestral stock which also gave birth to V. vulgaris).

It's a pity that the page devoted to this species remains empty, while this male is wrongly placed in V. pensylvanica. But maybe some other pictures will come this year.

If you don't trust me, you can submit this picture to Professor James Carpenter from the NMNH in New York. I'm certain he will confirm my ID. Yellowjackets are not so simple to identify at the specific level, and caution is especially needed with male specimens. But it makes them all the more fascinating.

By the way, I approve your project "through the lens" and congratulate you for your first worker photographs: with all specimens in the same position, comparison is especially easy. Eventually, when your set will be complete, you will state that I was right!

This should be below the following comment!
There is a contradiction with this ID and the key in Ayre (1):

couplet 5: head without a continuous yellow ring dorsally around eye...6
6: 1st antennal segment yellow ventrally....7
7: nothing fits!

or:
5: usually with a continuous yellow ring around eye; medial black mark on tergum 1 usually diamond shape...Western Yellowjacket.

I interpret ‘usually’ as ‘not always’. Abdominal pattern of this specimen fits Western Yellowjacket rather than Hybrid Yellowjacket (see Eric’s comment); Western also has yellow on 1st antennal segment , , as does this specimen. Hybrid Yellowjacket has black antennae.
BUT Ayre shows Western Yellowjacket not quite reaching Indiana, just eastern Illinois.
Verdict: my guess is Western Yellowjacket, assuming range has expanded since Ayre’s book.
Have relocated photo to Western Yellowjacket page; nothing is cast in stone and can just as easily be placed elsewhere.

Thanks to the quality of the photograph, three decisive criteria allow to identifiy this male at the specific level (that is, to separate it from its sister species V. vulgaris).
- the straightness of the black stripes between the frons (forehead) and the ocular sinuses.
- the yellowish, rather than grey, pilosity of the sides of the thorax (hence the species' "latin" name).
- the shortness of the pubescence of the abdomen.
Many males of V. vulgaris, at least in Europe, do have a virtually identical color pattern, but with the whole body much more hairy, with a lot of long black hairs on the top of the head and of the thorax, which are obviously lacking here.
Now, the challenge for Mr. Wagner is to take pictures of queen(s) and worker(s) of this rather unfrequent species.

Nice image of a male (note very long antennae). Odd pattern on the front of the abdomen, but yellow jackets can be highly variable in the balance of black and yellow markings.