586 



In seasons such as 1911, when investigations on the life-history were 

 being carried on, adult thrips appear in April and increase rapidly 

 during April and May, when the insects are largely congregated on the 

 fruit and foliage. From June to August they disperse over mis- 

 cellaneous food-plants. In August and September, migration back 

 to the citrus fruit takes place. The eggs deposited on stem and leaves 

 hatch during the following March or April. The average duration of 

 the egg-stage in summer varies from 10 to 18 days during May and 

 June, from 6 to 8 days in July and August and from 17 to 18 days in 

 September and October. The length of the larval stage varies from 

 6 to 13 days, and the pupal stage from 4 to 19 days. Pupation takes 

 place in crevices of bark, under dead leaves, etc. The most effective 

 method of control is the apphcation at high pressure of contact 

 insecticides, preferably those containing sulphur. Commercial lime- 

 sulphur of a density of 33° Be. should' be diluted with 50 times its 

 volume of water. Soda-sulphur solution gives equally good results. 

 Commercial tobacco extract should be used at the rate of 1 part in 

 800 parts of water. The greatest injury to the fruit is done between 

 the time the petals fall and when the fruit is half grown. Three 

 applications of insecticide are necessary during this period. The first 

 should be made when about four-fifths of the petals have fallen, the 

 second from 10 to 14 days later and the third from 2 to 4 weeks later 

 still. A fourth spray should be given in late August or September. 

 Nursery stock requires from 3 to 5 applications during the season, 

 the first being made between 15th April and 15th May. A table of 

 the quantities of liquid required is given, together with a short 

 description of spraying apparatus and cost of materials. 



Brooks (F. E.). The Houndheaded Apple-Tree Borer.— Z7. /S. Dept, 

 Acjric, Washington, D.C., Farmers' Bull. no. 675, 6th July 1915. 

 20 pp., 19 figs. 



The range of Saperda Candida (roundheaded apple-tree borer) in the 

 United States is bounded by a line extending from near the mouth of 

 the St. Lawrence westward to Minnesota, thence through Nebraska, 

 Kansas, Louisiana, Mississippi, Alabama and Georgia to the Atlantic 

 coast. This line, except in its soutn-western extent, bounds the dis- 

 tribution of the service tree, a favourite host of the borer. Orchards 

 near which service, wild crab or mountain ash trees grow, are thus very 

 liable to injury. Among cultivated fruits, apple, quince and pear are 

 most subject to attack. The adults issue from the trees in late spring 

 and early summer. Egg-laying begins about 10 days after emergence 

 and is continued for 40 Ox 50 days, each female depositing from 15 to 30 

 eggs. The eggs are placed in incisions in the bark, either above or just 

 below the soil. On hatching, the larvae attack the inner bark, then 

 boie into the sapwood in an upward direction. The adult stage is 

 reached in the third year. The pupal stage occupies about three 

 weeks ; the beetle emerges from the tree by a circular hole eaten through 

 the bark. The adults feed on the bark of twigs and on the midribs 

 and stems of leaves, and to some extent on the moisture contained in 

 the castings thrown from the trees by the larvae. The average life 

 of the beetle is about 40 or 50 days. The nataral enemies include 

 certain birds and a Hymenopterous parasite, Cenocoelius 'popidator. 



