14 BULLETIN 1225, TJ. S. DEPARTMENT OF AGRICULTURE. 



ADULT. 



DURATION OF LITE. 



The length, of life of the adult insects is extremely variable. A 

 series of 20 thrips becoming adult in the winter season from November 

 8 to February 8 (Table 3) lived an average of 82.85 days. The 

 longest life ran from November 12 to April 4, or 143 days, while 

 the shortest was 28 days, January 7 to February 4. A series of 20 

 thrips which became adult in August (Table 3) lived an average of 

 98 days. The longest was 196 days, August 24 to March 8, and the 

 shortest 41 days, August 24 to October 4. The average for these runs 

 higher than for those maturing in winter, several of them living over 

 four months. Field observations tend to confirm these results, for 

 many of the thrips maturing in summer hibernate, while those ma- 

 turing in winter live only long enough to start the breeding season in 

 spring. When kept without food the insects usually lived only 2 or 

 3 days, with an occasional specimen lasting 5 or 6 days. 



OVIPOSITION. 



Portion of plant selected. — The favorite place for depositing eggs 

 is in cracks or lesions of the bark resulting from the feeding of the 

 larvse or from injury from other causes. The eggs are sometimes 

 crowded into a small crack in large numbers, as many as 100 being 

 often observed. Some eggs are placed in the leaf axils or on leaf 

 scars and also along the bud scales. Another favorite place for 

 oviposition is on the end of a cut stem or limb. When trees were 

 pruned back in experimental work many eggs were deposited on the 

 upper ends of the stubs of the limbs. In the breeding jars in the 

 laboratory the favorite place for placing eggs was on the cut stems. 

 Eggs are sometimes forced down into the wood on these cut surfaces. 

 The end of a limb from a tree which had been pruned back for experi- 

 mental purposes was observed to have eggs on it, and when closely 

 examined under the binocular it was seen that several eggs had been 

 inserted between the layers of wood, some as deep as one-eighth 

 inch. Another place often selected for oviposition in the breeding 

 jars was along the stems just under the cotton surrounding them 

 in the vials. Under natural conditions the camphor thrips will 

 seldom lay an egg on an exposed smooth surface of a limb or leaf, 

 but always tries to select a crack in the bark or other place which 

 offers some protection. 



Description of process. — The act of oviposition has been observed 

 many times in the breeding jars. The eggs are quickly passed from 

 the body and seemingly with little difficulty on the part of the female, 

 the process usually requiring about two minutes. On one occasion 

 a thrips was seen to crawl up to a crack on the bark of a limb which 

 already contained 2 eggs, and place the end of her abdomen in the 

 opening near the eggs, remaining quiet for about 30 seconds. She then 

 turned around and brushed her antennae over the place a few times. 

 Again turning, she placed her ovipositor in the location selected and 

 at once deposited the egg. Some muscular contractions were ob- 

 served throughout the body, particularly in the abdomen, which was 

 also moved up and down. The abdomen then enlarged towards the 



