136 FAMILY IV. PHASMID.E. THE WALKING-STICKS. 



femorata, states that the young "moult but twice.' 1 Our knowl- 

 edge of the life history of other Orthoptera would tend to show 

 that this was an error and Severin has proven it to be so by rear- 

 ing 100 examples of the species under conditions as normal as 

 possible. He states (1911) that "23 per cent, moulted four times, 

 76 per cent, five times and only one per cent, six times." He adds 

 that since the insect usually eats parts, or all of its cast-off skin 

 it is possible that Riley overlooked some of the moults on this 

 account. He also states that those specimens "which moulted 

 four times reached sexual maturity on an average in 50 days, 

 while those which moulted five times required 57.5 days, on an 

 average before beginning the egg-laying period. * * * The 

 eggs, after passing out of the vaginal orifice, may be retained for 

 a number of hours within the peculiar 'external uterus' formed by 

 the ovipositor." 



The thick-thighed walking-stick appears to be abundant in any 

 certain locality only every other year. This is in part due to an 

 increase of the insect's natural enemies on those years in which 

 they are most abundant. These enemies are several species of 

 true bugs (Heteroptera), crows and other birds. The main reason 

 for the greater number of walking-sticks in alternate years is, 

 however, thought to be due to the fact that the larger proportion 

 of the eggs, especially those laid late in the autumn, take two years 

 in hatching. If at any time the insect threatens to become in- 

 jurious in woodlands, it can be held in check by burning the 

 leaves on the ground in the winter season, thus destroying the 

 hibernating eggs. 



53. DIAPHEEOMERA VELiEi Walsh, 1864, 410. Prairie Walking-stick. 



Form, size and color much as in D. femorata, the middle femora of 

 male not usually banded with gray as in that species. Head slightly more 

 elongate. Male with seventh abdominal segment no longer than ninth, in 

 femorata one-third longer; eighth segment two-thirds as long as seventh; 

 cerci with a very slender, sharp curved spine on inner side near base, in- 

 stead of a blunt tubercle as in femorata. Female with emargination at 

 apex of ninth abdominal segment deep, broadly rounded, in femorata more 

 shallow, triangular, with apex acute; subapical spine beneath the middle 

 and hind femora often very small. Length of body, $, 61, 9, 74; of 

 mesonotum, $, 14, 9, 16; of metanotum, <J and 9, 12; of hind femora, $ 

 and 9, 18 mm. 



Walsh's male type of this 'walking-stick Avas from Nebraska, 

 and one of his female cotypes from Illinois. Its main distribution 

 is west and southwest of the Mississippi, extending from Staples 



