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



HATCHING. 



When the egg is ready to hatch, the lateral halves split at their 

 juncture along its edge for about one-third the length from the 

 upper end, the nymph slowly forcing itself through the opening 

 thus made. 



ENEMIES OP THE EGG. 



The greatest natural check to the increase of the angular-winged 

 katydid in California is the egg parasite, Anastatus sp., already 

 referred to in connection with Scudderia furcata. Anastatus para- 

 sitizes a large percentage of all eggs deposited by this insect each 

 year. It is quite usual to find large batches of katydid eggs, each 

 egg showing the small, circular exit hole of the parasite (PI. IV, 

 fig. 1). It is, in fact, rare to find eggs of this katydid entirely free 

 from evidence of parasitism. Anastatus oviposits in the katydid 

 eggs in September and October, the larva feeding upon the egg 

 contents during the remainder of the fall and the adult emerging 

 the following spring. All reared specimens have emerged between 

 March 19 and May 18. It seems probable that 80 per cent or 

 more of all eggs deposited by M. rhombifolium are destroyed by 

 this little insect. For example, a lot of eggs collected in widely 

 separated locations in the fall of 1911 produced 43 adult Anastatus, 

 representing 86 per cent parasitism. Of another lot of 109 eggs 

 35 per cent produced living parasites and the remainder failed to 



hatch. 



The Nymph. 



description op instars. 



The nymph of the angular-winged katydid may be easily distin- 

 guished from that of the fork-tailed katydid by its plump body and 

 highly arched back, which gives it a decidedly humpbacked appear- 

 ance. The nymphs vary in length 

 from one-sixth to three -fourths 

 inch, depending upon the stage 

 of development. Their color is 

 grass-green throughout, including 

 the long, threadlike antennae. 

 There are six periods of develop- 

 ment, or ins tars, which may be 

 described as follows: 



Fig. 11. — The angular-winged katydid ( Microcen- -,. . n 



trum rhombifolium): First - instar nymph. FvTSt instCLV (fig. 11). MeaSUre- 



Slightly over twice natural size. (Original.) me nts: Length of body, 4 mm.; 



length of head (vertex to tip of jaws), 2 mm.; length of pronotum, 

 0.72 mm.; length of posterior femur, 4.75 mm.; length of posterior 

 tibia, 5 mm.; length of antenna, 16 mm.; subovate, convex along 

 dorsum and nearly flat along ventral surface. Color grass-green, 



