20 FIRST REPORT ON ECONOMIC BIOLOGY. 



and then one by one the pairs of legs are made free from their resting 

 position against the body. Swaying backward and forward, with legs 

 and antennae waving frantically about, the insect pushes out of the 

 egg- cavity almost to its full length, whereupon, leaning forward, it 

 eagerly takes a hold with its newly-formed feet, and, with a final effort, 

 pulls itself free, and walks rapidly away. From four to ten minutes 

 are required for the insect to free itself from the egg. The young 

 insect is almost transparent, and the green chlorophyll particles taken 

 into the stomach can be seen through the body wall. Growth is rapid 

 from the beginning. 



A very decided change takes place during the second larval stage 

 (Fig. 7). In about three weeks the insect reaches a size often larger 

 than that of the fully matured insect. It then ceases to feed, falls to 

 the ground, and enters the ground by some crack or wormhole. It 

 goes down from 3 to 10 inches, according to the structure and con- 

 dition of the soil, the usual depth being about 4 inches. Upon reach- 

 ing a secure depth, the larva hollows out for itself a tiny spherical 

 or oblong cell, or it finds an exceedingly small natural cavity, and 

 shapes this for its convenience. The completed chamber has a hard, 

 smooth inner wall, and it is about one-twelfth of an inch long, or just 

 a little longer than the insect itself. The insect here spends the greater 

 portion of its life. It remains for several months a quiescent, non- 

 food-taking larva. Later the pupal changes are undergone, and lastly 

 the adult insect appears before it issues forth to the tree. Larvae 

 collected from the ground on August 28th were active, and, strange 

 to say, green chlorophyll matter, undigested food, which had been 

 taken into the stomach several months before, was still present in 

 their bodies. The insects are scattered through the soil from near the 

 trunk to several feet from the tree." 



The Nymph or Pupa. Mr. Moulton has not been able to deter- 

 mine how long the nymph stage (Fig. 8) lasts, but it evidently extends 

 over several weeks. Nymphs in all stages of development were col- 

 'lected during May and at intervals until the following February, but 

 they are most common during December, January, and February. Mr. 

 Moulton has gathered nymphs from the ground early in May, but it 

 is difficult to explain their presence there so early in the spring. It 

 hardly seems possible that these were the still immature forms of 

 the previous year, for by this time all adult thrips have left the trees. 

 These nymphs were taken along with the larvae, which had just entered 

 the ground, and it might seem that they were hurrying through to 



