Black and Yellow Thrips - Flies - Spoil leaves and flowers. 

Minute small flies - Thrips - cause streaky marks on flowers and foliage. they suck at the leaf or flower in order to obtain the sap within. The marks are usually a silvery colour and are pronounced on Gladiolus flowers in particular. Very small insects - just visible - and are more active in hot dry weather.

Not a huge pest - unless you are going to 'show' your gladiolus blooms! Contact spray such as Bifenthrin will work as will the systemic insecticide  Provado.

Also known as Thunder flies, Storm Flies and Corn Lice.

A common Thrips shown for scale on a finger. (The singular and plural name are the same with Thrips!)