. Bulletin of the Department of Agriculture. Agriculture. 14 BULLETIN 616, U. S. DEPARTMENT OF AGRICULTURE. and from the latter part of September to November it will range from about 12 to 14 days. Table IV.—Seasonal variations in duration of the larval stage of the citrus thrips, Lindsay, Cal., 1911. Period of Prevailing mean tempera- tures. Mar. 25 to Apr. 15 May 13 to June 3. June 13 to Sept. 5. Sept. 4 to Sept. 21 Sept. 23 to Nov. 5 o F All four molts of the citrus thrips, comprising two in the larval stage and two in the pupal stage, are accompl
. Bulletin of the Department of Agriculture. Agriculture. 14 BULLETIN 616, U. S. DEPARTMENT OF AGRICULTURE. and from the latter part of September to November it will range from about 12 to 14 days. Table IV.—Seasonal variations in duration of the larval stage of the citrus thrips, Lindsay, Cal., 1911. Period of Prevailing mean tempera- tures. Mar. 25 to Apr. 15 May 13 to June 3. June 13 to Sept. 5. Sept. 4 to Sept. 21 Sept. 23 to Nov. 5 o F All four molts of the citrus thrips, comprising two in the larval stage and two in the pupal stage, are accomplished in about the same manner. The first molt takes place 0n the leaves and fruit of the host plant, the remainder in some secure hiding place, usually on the ground. When ready to molt the larva ceases to feed and becomes inactive. Tremors vibrate the antennae and body at brief intervals for a period of from one to three hours, and the abdomen slowly con- tracts and shrinks away from the old skin. Then follows an active period of from 15 minutes to an hour, in which the middle and hind legs are repeatedly stretched as far back as possible and slowly drawn forward, while the insect goes through jerky lateral motions with the body. The skin then splits from the vertex along the dorsum to the abdomen, after which the insect becomes very active, doubling down with the head between the fore feet and slowly re- moving the skin from the head and antennae. The legs are then worked out of their casings and the exuvium pushed back under the body. The skin usually is attached at the tip of the abdomen to the surface on which molting occurs, greatly aiding the insect in ex- tricating itself. The skin generally is removed entire, but occa- sionally antennal and leg casings are removed separately. Cool weather greatly retards the process, which is more likely to be ob- served when such weather prevails. Groups of larval skins re- sembling specks of gray dust sometimes are found on orange
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