Learn Hardcore Italian: In giardino vedo un insetto colorato su un fiore. - In the garden I see a colorful insect on a flower.

In Italian, when you speak of being in a place in a general sense, you often drop the article and just say in + noun. So in giardino means “in the garden” in a non-specific, generic way. If you wanted to specify a particular garden, you could say nel giardino (in + il giardino).

Why is the subject pronoun io missing before vedo?

Italian is a pro-drop language: the verb ending -o in vedo already tells you the subject is “I.” Adding io (I) is grammatically correct but redundant and used only for emphasis or contrast.

Why do we use un before insetto instead of uno?

Italian has two masculine singular indefinite articles: un and uno. You use uno before nouns beginning with s+consonant (e.g. s+z) or z, gn, ps, x, y. Insetto begins with a vowel (i), so you use un.

Why is colorato placed after insetto? Could it come before?

Most descriptive adjectives, especially colors, follow the noun in Italian. So insetto colorato is the normal order. You can say un colorato insetto for poetic or emphatic effect, but it sounds less natural in everyday speech.

Why is su used to mean “on” here? What about sopra?

Su is the standard preposition for “on” or “upon” in Italian everyday usage. Sopra also exists and often emphasizes “above” or “over,” but in this simple locative sense, Italians nearly always say su.

How would the sentence change if there were two insects?

You need to make both noun and adjective plural:
In giardino vedo due insetti colorati su un fiore.

What if the insect were feminine, like ape (bee)?

You must match gender and adjust the article. Since ape is feminine and begins with a vowel, you elide una to un’:
In giardino vedo un’ape colorata su un fiore.

Why is the simple present vedo used, rather than an equivalent of “I am seeing”?

Italian doesn’t have a separate continuous (progressive) form. The simple present covers both “I see” and “I am seeing” contexts.