1920] 



ECONOMIC ZOOLOGY — ENTOMOLOGY. 555 



posts in Floiidn. the author tlivkles the State into zones based upon tempera- 

 ture records of the U. S. Weather Bureau. 



In the tirst zone, comprising the citrus producing counties of Putnam, Volusia, 

 and Marion, witli parts of Lal^e and Orange in which tlie t«'m[)erature varied 

 from 15 to 20' F., tliere was practically complete defoliation of all citrus trees, 

 many grapefruit trees were killed to the ground, ayd oranges were killed back 

 to within 4 to 8 ft. of the ground. In the second, or next warmer zone, com- 

 prising the renuxiuder of the counties of Lake and Orange, and the counties of 

 Osceola, Polk, De Sota, IManatee, and Lee, in which the minimum temperature 

 varied from 20 to 25" F., the percentage of bearing wood killed varied from 

 20 to 40 with oranges and 25 to 50 with grapefruit. In this zone, there \vas 

 abf)Ut 90 to 05 per cent defoliation of orange trees except in a few protected 

 places, and the grapefruit trees were completely defoliated. In the third, or 

 warmest zone, comprising the counties of Pinellas, Dade, Palm Beach. 

 St. Lucie, and part of Brevard in which the minimum temperature varied 

 from 25 to 30°, the percentage of bearing wood killed varied from to 15 for 

 oranges and from to 20 for grapefruit. In this third zone, defoliation was 

 not sufficient to influence the number of white flies to a degree to be of eco- 

 nomic importance. 



While the citrus white fly survives on privet in the temperatures of North 

 Carolina, and the recent cold wave did not injure this species in Florida, the 

 defoliation of the citrus trees resulted in reducing the number in many places 

 and localities to the point of almost complete extermination, particularly in 

 zone 1. The cloudy-winged white fly, which infests only citrus and is found 

 largely on grai)efruit, was destroyed only in proportion to the extent of the 

 defoliation. The purple, scale was almost exterminated in the counties of 

 zone 1, but the eggs were not frozen sufficiently to keep them from hatching. 

 It also received a complete setback in zpne 2, but not to the extent it did iu 

 zone 1. In zone 3, the number was greatly i-educed but not sufflciently to make 

 spraying unnecessary. The red scale on camphor {Chnjsomphalus aonklum L.) 

 was injured in nearly all stages except the egg by the frost, and not more than 

 one insect in 10,000 or more survived. The rust mite (Eriophycs olcivorus 

 . Ashm.) was partially frozen and partially killed because the foliage was shed. 

 ! It was nearly exterminated in zone 1, severely set back in zone 2, and tjiough 

 1 greatly reduced in number in zone 3 not sufRoieutly to be of much economic im- 

 portance. The adults of the i>urple mite (Tctranyclius cilri McGr.) did not ap- 

 pear to have been hurt. The eggs, however, are thought to have been affected, 

 since the pest has not been very abundant since the freeze. 



A brief accoinit is also given of the effect of the freeze on the pests of other 

 plants than citrus. The spider mite Tcnuipalpus biocuhitus INIcGr. was but 

 slightly injured by the cold, while Tctranychtis yothcrsi McGr. on camphor 

 appeared to have been seriously affected. 



Work on citrus insect pests [in Porto Rico] (War Dept. [U. S.], Ami. 

 Rpt. Governor P. R., 19 (1910), p. 695). — A number of insects that have not 

 previously been recorded from Porto llico have been found breeding ui)on citrus 

 foliage, as follows: The star scale (Vinsonia stcllifcra [Westw.]), a common 

 pest of mango, coconut, and pomarosa at Rio Piedras, also observed on cattleya 

 orchids; Orntenis pyymwa Fab., which heavily infests citrus sprouts, particu- 

 larly in June, and breeds abundantly upon the wild bushes Cordia corymbosa 

 and C. cylindrostachya, also upon young coffee foliage and the passion fruit 

 vine; an undetermined orange-brown thi'ips; two mealy bugs, one very close to 

 PseiidococcuH longispinus, the other ai)parently the citrophilus scale; a bn"? 

 worm ; and a larva of au undetermined arcteid moth. 

 U.^G'— 20 5 



