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PROCEEDINGS OF THE THIllD ENTOMOLOGICAL MEETING 



is inconspicuous and is dark ; all the legs are well-developed. It 

 measures about 21 mm. in length. 



When full-grown the caterpillars begin to spin the very loose web-like 

 shelter between the twigs or on the leaf, and turn to pale yellow pupae 

 in it. The pupa is gradually tapering to an obtuse anal angle, with a 

 row of blackish spots on each segment. The length is about 11 mm. 



In about ten or eleven days after pupation the moth emerges and 

 begins to deposit the eggs. The breeding data are as in the following 

 table : — 



The eggs of the second brood were not deposited by a female of the 

 first brood, but by a female collected in the orange-tree field. 



The above table shows that this insect has probably three or four 

 generations in a year in Formosa. 



This very plentiful Formosan moth can hardly be called a pest of 

 the plants already mention e:l, although it is usually well-known as a 

 minor pest of them. 



No. 41. — Bistun marginata, Mats. [Kurozu-Yedashaku.) 

 This Geometrid is commonly found in April in the districts of Kimpori 

 and Tamsui in Taihoku-Cho, and its occurrence is often so abundant 

 that there is no vestige of green on the tea-bushes throughout a large 

 plantation, but it is quite restricted to these two districts according 

 to our past investigations. 



The greyish moth usually emerges in March and the female deposits 

 her eggs on the twig or trunJi in a large mass (10 X 5 mm. — 35 X 15 mm.) 

 ■covered -with her pale brownish anal tuft-hairs, immediately after emer- 

 gence. The eggs are short- elliptical, about 0-8 mm. in length and are 

 pale greenish-yellow but become green towards hatching. The 

 tiny larvse hatch in two or three days, and begin to hang down by a 

 fine thread sent forth from their mouths, and the thread is blown by 

 the wind until another bush or twig is reached. This method of moving 

 is done by almost all newly hatched larvse, with the exception of those 

 that find suitable leaves soon after they are hatched. They almost 

 always live singly and eat the leaf irregularly from the margin. The 

 duration of each instar is from about five to ten days. 



