1878.] 



AND HORTICULTURIST. 



213 



name for any new or curious tree or shrub, which every sort known in this zone ; and artists who 

 they happen to fii'd on their farms, can do so by j wisli to delineate any particular foliage can here 

 a walk in the Arboretum. Those designing to j find every specimen.— i-'nnV and Floral Maga- 

 ornament their lanes and grounds can here see Zine. 



Natural HisroRriND Science. 



COMMUNICA riONS. 



JUMPING BEANS OF MEXICO. 



BY PROF. C. V. RILEY. 



Mr. Riley exhibited certain seeds which pos- 

 sessed a hidden power of jumping and moving 

 about on the ta])le. He stated that he had 

 recently received them from Mr. G. W. Barnes, 

 of San Diego, Cal., and that they were generally 

 known by the name of Mexican Jumping Seeds. 

 They are prolxably derived from a tricoccous 

 euphorbiaceous plant. Each of the seeds meas- 

 ures about one-third of an inch, and have two 

 flat sides, meeting at an obtuse angle, and a 

 third broader, convex side, with a medial carina. 

 If cut open, each is found to contain a single fat, 

 whitish w.orm, which has eaten all the contents 

 of the seed and lined the shell with a delicate 

 carpet of silk. The worm very closely resem- 

 bles the common Apple Worm {Carpocapsa po- 

 monella , and, indeed, is very closely related, the 

 insect being known to science as Carpocapsa sal- 

 titans. It was first recorded by Westwood in 

 the Proceedings of the Ashmolean Society of 

 Oxford, in 1857 (t. 3, pp. lo7-S), and repeatedly 

 referred to under the name of Carpocnsap Dehai- 

 siana in the Annales of the French Entomolog- 

 ical Society for 1859. The egg of the moth is 

 doubtless laid on the yovmg pod which contains 

 the three angular seeds, and the worm gnaws 

 into the succulent seed, which, in after growth, 

 closes up the minute hole of entrance, just as in 

 the case of the common Pea Weevil (Bruchus 

 pisi). Toward the month of February the larva 

 eats a circular hole through the hard shell of its 

 habitation, and then closes it again with a little 

 plug of silk so admirably adjusted that the future 

 moth, which will have no jaws to cut with, may 

 escape from its prison. A slight cocoon is then 

 spun within the seed, with a passage-way leading 

 to the circular door ; and the hitherto restless 

 larva assumes the quiescent pupa state. Shortly 

 afterwards, the pupa works to the door, pushes 

 it open, and the little moth escapes. When ripe, 

 the shell is very light, and, as the worm occu- 

 pies but about one-sixth the enclosed space, the 



slightest motion will cause the seed to rock from 

 one of the flat sides to the other. But the seed 

 is often made to jerk and jump, and, though this 

 has been denied by many authors, Mr. Riley had 

 had abundant proof of the fact, and had seen the 

 seed jerked several lines forward at a bound, and 

 raised a line or more from the surface on which 

 it rested. If the seed be cut, the worm will soon 

 cover up the hole with a transparent membrane 

 of silk ; and if two of the opposite angles be cut, 

 the movements of the worm can then be seen, if 

 the seed be held against the light. It then be- 

 comes evident that the jerking motion is con- 

 veyed by the worm holding fast to the silken 

 lining by its anal and four hind abdominal pro- 

 legs, which have very strong hook.s, and then 

 drawing back the forebody, and tapping the 

 j wall of its cell with the head, sometimes thrown 

 I from side to side, but more often brought directly 

 down as in the motion of a wood-pecker's head 

 when tapping for insects. In drawing back 

 the forebody the thoracic part swells, and 

 the horny thoracic legs are withdra^vn so 

 as to assist the jaws in receiving the shock of 

 the tap, which is very vigorous, and often given 

 at the rate of two a second, and for twenty or 

 more times without interruption. It is remark- 

 able that this, of all the numerous seed-inhabiting 

 Lepidopterous larva?, should possess so curious 

 a habit. The seed will move for several months, 

 because, as with most Tortricidous larvae, this 

 one remains a long time in the larva state after 

 coming to its grow^th and before pupating. 



Mr. Barnes gives the following account of the 

 plant, received through Capt. Polhamus, of 

 Yuma, A. T. It seems to be called both Yerba 

 deflecha and Colliguaja by the Mexicans: 



"Arrow-weed ( Yerba de flecha).— This is the 

 name the shrub bears that produces the triangu- 

 lar seeds that during six or eight months have a 

 continual jumping movement. The shrub is 

 small, from four to six feet in height, branchy, 

 and in the months of June and July yields the 

 seeds, a pod containing three to five seeds. 

 These seeds have each a little worm inside. 

 The leaf of the plant is very similar to that of 



