14 BULLETIN 256, U. S. DEPARTMENT OF AGRICULTURE. 



larly bad in 1911 and 1912 large numbers of adult katydids disap- 

 peared in August and September. At about the same time large 

 numbers of small birds of an undetermined species were noted in 

 and about these orchards. These little birds were unquestionably 

 responsible for the disappearance of katydids. 



Seasonal History. 



As there is but one generation of the fork-tailed katydid annually, 

 the duration of the life cycle is approximately one year. The aver- 

 age life cycle, as determined from a number of complete rearings in 

 1911 and 1912, was 367 days, ranging from 343 to 383 days. The 

 first nymphs to appear issued about April 20, the majority issuing 

 during May. Nymphs are most abundant in May and June, but 

 have occasionally been seen as late as August 15. The first adults 

 appear early hi June, are fairly numerous by the last of June, and 

 most abundant during July and August. They can be found with- 

 out much difficulty hi September and more rarely in October. The 

 last specimens of the season were captured December 3. A few 

 have been kept alive in screen cages until early January. 



THE ANGULAR- WINGED KATYDID. 



NATURE AND EXTENT OF INJURY. 



The angular-winged katydid (Microcentrum rliombifolium, Sauss.) 

 somewhat closely resembles the fork-tailed katydid and is closely 

 associated with the latter on orange trees in the San Joaquin Valley. 

 It is, however, larger than the fork-tailed katydid and may be readily 

 distinguished from that insect by its size, broader wings, and hi the 

 nymph by its hunchbacked appearance. Although responsible for 

 a certain amount of injury to orange trees annually, it attacks only 

 the foliage and rarely does enough damage to cause alarm. This 

 insect has been present in Florida orange groves for years without, 

 except in rare cases, causing sufficient damage to attract attention. 

 This is also the case in California. The observations of the writers 

 indicate that the minor position of the angular-winged katydid as a 

 pest is largely due, first, to the high percentage of parasitism suffered 

 by the eggs; and, second, to the fact that the insect does not attack 

 the fruit. That it might injure the fruit if able to increase to the 

 point of crowding is quite possible. The insect is also exposed to 

 the attacks of various enemies, chiefly birds, because of its large size 

 and slowness of movement. The first-instar nymphs feed principally 

 if not wholly upon the leaf surface, removing merely a chlorophyll 

 layer. Later stages gnaw clear through the leaves, filling them with 

 ragged holes, and destroy a larger amount of foliage in proportion 

 to their number than does the fork-tailed katydid. The insect has 

 never been seen to attack blossoms or fruit. 



