10 THE PEAR THRIPS. 



ally heavy driving rains, and we were unable in many cases to deter- 

 mine the amount of injury done by the thrips and the amount caused 

 by the rain, except in those places where injury done by the insects 

 was noticed before the rains came on. The damage, however, will 

 aggregate many thousands of dollars. 



LIPE-HISTORY AND HABITS. 



The Egg, the Ovipositor, and the Placing of the Egg. — The egg is bean- 

 shaped, is almost transparent, and when seen within the body of the 

 adult female is very large in proportion to the 

 size of the abdomen. It can be seen only with a 

 powerful lens or microscope. 



The ovipositor — the organ fitted for cutting 

 an incision in the plant tissue and for convey- 

 ing eggs from the abdomen of the adult female 

 into this incision — is made up of four distinct 

 ^'"of' thr'ips"'sholiu|'"ovi- plates, each of which has a serrate outer edge, 

 positor, greatly enlarged, is pointed, and is Operated by powerful muscles 

 and plates within the abdomen. (See Fig. 5.) 

 -^ In placing an egg, the thrips first tears or weakens the plant epi- 

 dermis by means of the mouth parts, takes a step forward, and, arching 

 the abdomen a little, lowers the ovipositor from its sheath in the last 

 two abdominal segments, almost at right angles with the body, and by 

 operating the tiny saws up and down, she enlarges the opening and 

 cuts a quite deep incision. When this is finished an egg is forced down 

 through the space between the four plates and into the cavity below, 

 underneath the plant epidermis. The operation of making the incision, 

 of depositing a single egg, and of withdrawing the ovipositor requires 

 from four to ten minutes, and has been observed many times. One 

 often finds a branch or a whole tree where almost every female will be 

 depositing eggs at the same time. For depositing eggs, the tiny and 

 very tender stems of blossoms and leaf petioles are preferred, and as 

 the leaves develop the midrib and veins on the lower side of the leaf 

 are chosen and later the tissue of the leaf itself. It has been stated by 

 other observers that the feeding and depositing of eggs go together; 

 indeed, the destructive work of the ovipositor is quite as effective as 

 the injury caused by feeding, for the cutting of numerous incisions into 

 a tiny stem greatly weakens it. We have seen the stems of cherries 

 and prunes so injured in this way that, after the fruit becomes almost 

 half grown, the stem weakens and the fruit falls. 



The insect always chooses the tenderest parts of a plant for oviposi- 

 tion, and this with reason. If the tissue is hard there is danger of the 

 ovipositor becoming fastened so that it can not be withdrawn. Also, 



