SPRING AND SUMMER NUMBERS 53 
THYSANOPTERA OF FLORIDA 
J. R. WATSON 
Agricultural Experiment Station 
These insects are usually called thrips. They are all small, 
the largest measuring about eight millimeters (1/3 in.) in 
length while the smallest is scarcely half a millimeter. The vast 
majority are from one to two millimeters long. This is not as 
great a range in size as is common in other orders of insects. 
They are slender insects and their bodies are composed of four 
movable parts—the head, prothoraz, pterothorax (fused meso- 
and meta-thorax), and abdomen. This mobile structure enables 
them readily to squeeze into cracks in the bark of trees and into 
the parts of flowers where most of them live. Moreover the ten 
joints of the abdomen are loosely articulated so that the abdo- 
men, like that of rove beetles, can be bent up over the back in a 
threatening manner as if the insect would sting. The real ob- 
ject of the motion is, in most cases, to straighten out the hairs: 
of the wings preparatory to flight. 
Each of the four parts of the body bears appendages. On 
the head are the antennae, always long and slender and com- 
posed of from seven to nine segments and capable also of a 
large range of motion. The comparative lengths of these anten- 
nal segments are much used in classifying thrips. On the an- 
tennae are hairs and spine-like organs. Some of these are 
“sense cones’, probably organs of smell and perhaps of hearing. 
Large compound eyes are present and near them usually 
three small simple eyes, ocelli. The anterior one of these fre- 
quently is directed forward and the others upward. 
The mouth parts are of the sucking type and not rasping as 
is sometimes stated. However, the punctures they make in the 
tissues attacked are usually numerous and close together, giving 
to the injured tissues somewhat the appearance of having been 
rasped away. A peculiar characteristic of the mouth parts is 
the lack of symmetry between the two sides. The right mandi- 
ble is entirely missing. 
Although some species are wingless, there are usually two 
pairs of similar wings. Each consists of a long and rather nar- 
row membrane fringed with very long hairs. These hairs are 
responsible for the name Thysanoptera, “fringe wings’. In 
