KATYDIDS INJURIOUS TO ORANGES IN CALIFORNIA. 19 



DURATION OF INSTARS. 



The average duration of the nyniphal instars of the angular- winged 

 katydid, as determined from a number of individual rearings, was as 

 follows: Instar I, 13.8 days; instar II, 8.6 days; instar III, 9.5 days; 

 instar IV, 10.2 days; instar V, 13.7 days; instar VI, 17.2 days. The 

 average duration of the complete nymphal stage is therefore 73 days, 

 or about 2\ months. Molting is accomplished hi about the same 

 manner as by the fork-tailed katydid (see pp. 10-11. The nymph 

 always eats the greater part of its cast skin after each molt, rejecting 

 only the mandibles, claws, and certain hard parts of the head cast. 



The Adult. 



general appearance. 



The body of the adult is broad and compact, and comparatively 

 very wide dorsoventrally (PI. IV, fig. 2). The humpbacked appear- 

 ance so characteristic of the later stages of the nymph is retained, but 

 to a lesser degree, owing to the broadly rounded angle of the fore- 

 wings. The hind wings extend the full length of the body beyond 

 the tip of the abdomen. The color is uniform grass-green over most 

 of the body, becoming yellowish green on the ventral surface. The 

 insect is fully 2 inches long, the wings measuring, when spread as for 

 flight, about Z\ mches. 



MATING. 



Mating rarely or never occurs earlier than 18 days after emergence, 

 and the period between emergence and the first union of the sexes 

 ranges from 18 to 26 days. Coitus is succeeded by the extrusion of 

 a small, bilobed mass of albuminous material, which, as hi Scudderia 

 furcata, may be seen clinging to the abdomen at the base of the 

 ovipositor in the female for several hours subsequent thereto. The 

 favorite time for mating is at night, when the males are very active 

 and may often be hoard sending forth a loud and sustained clatter 

 for several hours at a time. The stridulating note, once heard, is 

 readily recognized, and to traco it to its source will often disclose both 

 male and female katydids, as stridulation appears to be closely con- 

 oected with courtship. The stridulating song of an allied species, 

 Microcentrum retinerve Burm., has been described by Riley as con- 

 sisting <>f "a scries of from 25 to 30 raspings, as of a stiff quill drawn 

 file" at the rate of "about five of these raspings or trills per 



ond, ;ill alike, and with equal intervals, * * * the whole 



strongly recalling i he slow i liming of a child's rattle." This descrip- 

 tion is equally applicable to M. rhombifolium. 



OVIPO ill". \ WD i.i.'.'i i if OF ADULT LIFE. 



In captivity females have deposited from •'» to L 23 eggs each during 



