List form:
In your question, you provided an ordered list.
In list form, I would only use the colon.
There are two types of insects:
a) white
b) black
Sentence form:
1) In addition to the semicolon and colon, you could also use a comma. This is simpler and more common than the semicolon.
There are two types of insects, white
and black.
I prefer commas when there is a dependent clause afterwards.
There are two types of insects, white
and black, on my kitchen table.
2) When using the semicolon, I would expect other commas which would create ambiguity or confusion. However, in this case, it would be the most complicated option, and it is better to avoid it and better to create another sentence instead of an unwieldy one.
With commas:
There are two types of insects, moths,
the white insects, and beetles, the
black insects.
There are two types of insects, moths,
the white insects, and beetles, the
black insects, on my kitchen table.
With semicolons:
There are two types of insects; moths,
the white insects; and beetles, the
black insects.
There are two types of insects; moths,
the white insects; and beetles, the
black insects; on my kitchen table.
In another case, I would use a semicolon for independent clauses:
There are two kinds of insects; the
white insects and the black insects
are on my kitchen table.
From Nishant's example, I would put a comma before the conjunction between "the white insect is white in color" and "the black insect is black in color" because they are two independent clauses:
There are two kinds of insects; the
white insect is white in color, and
the black insect is black in color.
3) The colon is the other useful option besides the comma.
You can use a colon for lists.
There are two types of insects: white
and black.
However, if a dependent clause comes afterwards, it changes the meaning of the sentence.
There are two types of insects: white
and black, on my kitchen table.
This above sentence says that there are only two types of insects in existence, and they all live on "my kitchen table".
If you wanted the same meaning as "There are two types of insects, white and black, on my kitchen table", then you would have to move the dependent clause before the colon.
Recommended:
On my kitchen table, there are two
types of insects: white and black.
Try to keep the colon as close as possible to what it is listing about.
Unrecommended:
There are two types of insects on my
kitchen table: white and black.
Although the above sentence is unrecommended, it is still correct because logically, a list of two items (white and black) will describe the "two types of insects" rather than the one kitchen table.
It is grammatically correct, as L.L.C. is an acronym, and Co. is an abbreviation; but it is certainly not the only correct option. LLC is far more common than L.L.C. in company names, though Co is not as popular as Co.
I would therefore expect to see:
Xyz Trading Co. LLC
For examples, you can google "co llc" (google ignores caps and punctuation), and see what comes up.
Wikipedia has a discussion on the use of punctuation with acronyms and abbreviations; generally, either way is grammatically acceptable (with few exceptions), though periods are definitely not as popular.
Best Answer
If you’re addressing Bill, the question doesn’t arise, because we don’t use commas in speech. In writing, I invited my cousin, Bill suggests, as you say, only one cousin, whereas I invited my cousin Bill suggests there might also be cousins Jane and Andrew and perhaps more besides. If you’d organized some occasion for your extended family, and you said I invited my cousins Bill, Jane, and Andrew that, by analogy, might suggest that they you had cousins who were not invited. On the other hand, I invited my cousins, Bill, Jane, and Andrew might suggest that they were all the cousins you had. In practice, there are likely to be other clues in the linguistic and social environment helping to resolve any ambiguity.
You probably know that the use of commas in this way, and the designations ‘restrictive’ and ‘non-restrictive’ (alternatively, ‘defining’ and ‘non-defining’) are more usually applied to relative clauses. In the sentence I invited my cousin who lives in Australia, the clause who lives in Australia is restrictive and leaves open the possibility of cousins elsewhere. In I invited my cousin , who lives in Australia, the clause who lives in Australia is non-restrictive, and doesn’t. (The authors of ‘The Cambridge Grammar of the English Language’ use the terms ‘integrated’ and ‘supplementary’, which seem preferable.)