625 
and are laid horizontally along the back when at rest. The meta- 
morphosis is incomplete. The mouth parts are probably used chiefly 
for sucking; they are intermediate in form between those of the 
sucking and those of the biting insects—i.e., they are fitted to pierce 
and to suck. 
There are various species in this State, and some are very de- 
structive to onion tops. Onions. attacked by thrips will soon have 
a whitish appearance, and the onions themselves will often become 
stunted in growth. They also attack orange and lemon trees, feed- 
ing on both the upper and lower surface of the leaves, and giving 
Cluster of oranges infested with Dactylopius citri. 
to them a very whitish appearance. Where they appear they do 
some damage if early rains fail, as then the leaves become less juicy 
and palatable for them and they betake themselves to the fruit. 
They are extremely lively, leaping or taking flight with great agility. 
Some species eat other inseets, but the most live upon vegetation. 
