March 4, 1891.] 



Garden and Forest. 



99 



small, pleasantly fragrant flowers borne on a slender scape. It 

 is nearest B. Mr turn, but neither the pseudo-bulbs nor the 

 leaves are known. The plant was common, and the flowers, 

 which are highly prized by the Shan maidens for ornamenting 

 their hair, were' sold in the bazaars, so that General Collett 

 thought it must be known in Europe and was satisfied with 

 bringing away two or three inflorescences. 



A new Lily {Lilium Bakerianum) may close my remarks on 

 this collection. It is intermediate in character between L, 

 Dahuricum and L.Japonicum. 



Doubtless, a country so rich in ornamental novelties as the 

 Shan States will soon be explored by the collectors of some of 

 our nurserymen. 



Kew. 



W. Bolting Hemsley. 



The Chollas. 



ONE of the most characteristic features in the landscape 

 of southern California, especially in the region of the 

 Coast, is the extensive, impenetrable thickets of a cylindrical 

 species of Cactus, familiar to all under the Mexican name, 

 Chollas. The common Cholla in the vicinity of San Diego is 

 Opunlia prollfera, Engelm., which grows abundantly on arid 

 hills or mesas, especially on precipitous canon-slopes bor- 

 dering the usually dry water-courses. Chollas Valley, within the 

 limitsof the city of San Diego, received its name from the abun- 

 dance of this plant. It grows from three to eight or ten feet in 

 height, the stems from two to four, rarely six or seven, inches 

 in diameter, and at the base forming a woody stem or trunk a 

 foot or more in diameter. 



The plant has never been utilized by stockmen for forage to 

 my knowledge, as has been the case with some species of the 

 genus, and "it is quite a formidable task to clear land of 

 this obnoxious plant. The short, stout spines are especially 

 painful and tenacious after they have entered the flesh, and 

 strangers in our land, human and brute, soon learn to give it 

 a wide berth. 



The flowers are an inch and a half in diameter, of a pretty 

 wine or pomegranate purple, but are so well guarded by a 

 multitude of formidable spines as to almost repel admiration. 

 The fruit is proliferous, the seed almost invariably abortive. 



Professor E. L. Greene records it from the Coronado and 

 Guadalupe Islands, while T. S. Brandegee reports it from the 

 Santa Catalina Island and as far southward as San Ignacio.in Low- 

 erCalifornia, where, he says, "the plants aresometimesalmost 

 spineless." 1 have not found it south of Todos Santos Bay, 

 Lower California, but to the southward a very similar Cactus 

 appears, identical in appearance, but very distinct in its fruit. 

 I am, therefore, inclined to doubt whether the species which 

 Mr. Brandegee reports or Professor Greene's Guadalupe 

 Island plant, which he says is "smaller than in California," 

 is the same as our San Diego species. The fruit is fleshy, 

 spinous, very rarely containing even a single seed. The per- 

 fect seed is much larger than in the above-mentioned Mexican 

 species. 



Opunlia serpentina, Engelm., is a slenderer, usually pros- 

 trate, species, not gregarious nor so abundant as 0. prolifera, 

 producing yellowish green, purple-tinged flowers, followed by 

 a dry many-seeded fruit, broadly umblicated and very spiny. 

 The stems'of this plant are seldom more than three or four 

 feet long, an inch or two in diameter, and less woody in struc- 

 ture than the last species. 



On the Colorado desert and eastward and southward through 

 Arizona and New Mexico into old Mexico, the species and 

 varieties of Chollas seem almost endless in number. The 

 Indians in the mountains of San Diego County and in northern 

 Lower California formerly planted them above the graves 

 of their dead, and often a valley may be found dotted over 

 with little groups of a slender, erect species (probably 0. Ber- 

 nardina, Engelm., ined.) planted by their hands. 



One species (O. Bigelovii, Engelm.) has been sparingly util- 

 ized as fodder for cattle, after the spines had been burnt off, 

 but all the species are very generally detested by all ■who are 

 brought into intimate relations with them. 



San Diego, Cal. C.K. Orcutt. 



An Insect Pest of Cattleyas. 



(Isoso/na orchideartcm.) 

 ''T^HIS insect does not appear as yet to have become common 

 -*- orgenerally known amongcollections in thiscountry, and it 

 is well that growers should be on their guard against it, because 

 it seems to have become quite common in Europe, and is 

 therefore liable to be introduced with any fresh importation of 

 the plants. 



The pest has appeared in more than one locality and in 

 past years has not been unknown even in such carefully guarded 



collections as those of Mr. Ames, at North Easton, Massachu- 

 setts. A notice of its occurrence in another collection appears 

 in Insect Life, vol. ii. (1890). 



About two years ago, Dr. C. G. Weld, of Brookline, Massa- 

 chusetts, imported a lot of Cattleyas from England which at 

 first appeared to start into good healthy growth, but soon 

 proved to be badly infested by this so-called "orchid-fly." 

 The young buds or pseudo-bulbs which would eventually 

 produce the flowering-spikes were noticed to become checked 

 in their development, and upon cutting them open numerous 

 little maggots or larvae were found in cavities which they had 

 eaten. Some pupae were also found, and these, together with 

 a few of the larvae, afterward developed into small, black, four- 

 winged flies. 



From an investigation of the history of this insect it would 

 appear that it was first publicly referred to by Professor J. O. 

 Westwood at the meeting of the Royal Horticultural Society of 

 February 16th, 1869, and a brief mention of the fact was given 

 on page 196 of the Gardeners' Chronicle for the same year. 

 On page 1230 of the same volume (1869) Professor Westwood 

 gave a slight sketch and a brief notice of the insect, for which 

 he proposed the name of Isosoma orchidearum. It is more 

 fully figured and is technically described by the same author 

 in the Transactions of the Entomological Society of London for 

 1882, pp. 322-324, pi. xi'ii.; and occasional brief notices of the 

 pest have appeared in various foreign journals. 



The perfect insect or fly is black, and has clear, shining, 

 iridescent wings. The female is about one-seventh of an inch 

 long, while the male is considerably smaller, being only about 

 one-tenth of an inch in length. The head and thorax are 

 rough and unpolished, the microscope showing them to be 

 covered with tiny pits, from each of which little bristles or 

 hairs project. The abdomen is black, smooth, polished and 

 shining, and is without hairs except on the smaller last seg- 

 ments. The abdomen of the female is pointed and somewhat 

 wedge-shaped beneath, while that of the male is small, being 

 not more than half the length of the female abdomen and ter- 

 minating bluntly or abruptly. Under the microscope the sexes 

 may be readily separated by the antenna;. In the female most 

 of the joints are about of the same size and shape, being sym- 

 metrical and connected together by inconspicuous pedicels ; 

 while the male antennae are somewhat longer, the chief joints 

 being longer and abruptly tapering to a slender neck or pedicel 

 at the anterior ends, and lacking symmetry by being much 

 more swollen on one side than on the other. The whorls 

 of hairs or bristles are very much longer than on female 

 antennae. 



It may be also worth noting that, counting the less distinct 

 articulation in the terminal joints, the antennae of the females 

 are apparently ten-jointed, while in the males only nine divi- 

 sions are noticeable. 



The legs at the joints are red ; the femora or thighs black ; 

 the tibiae or middle portion yellowish or reddish, except on the 

 hind pair, where they are blackish, and the feet (tarsi) are pale 

 or dull white and tipped with minute dark claws. From the 

 specimens' collected the females appeared to greatly outnum- 

 ber the males. 



The female is provided with a long and extremely slender 

 ovipositor, which it inserts into the tissue of the plant when 

 depositing its eggs. When not in use, this ovipositor lies quite 

 concealed by a groove and protecting sheaths, and only very 

 careful manipulation with a slender-pointed instrument will 

 bring it into view. In the figure the ovipositor and free por- 

 tion of the sheaths are shown removed from their closely fit- 

 ting position along the under side of the body. 



The little footless grubs or maggots are white, and a sixth of 

 an inch or less in length when fully grown. 



Several of them may be found together, and they change to 

 pupae, and eventually to the winged state, within the cavity 

 they have made in the Orchid, out of which they emerge 

 through a small round hole in the side. Owing to their small 

 size the flies are not easily detected after they escape, but they 

 have been found resting on the under side of the leaves of the 

 plants. 



If this insect once gets a foothold in a collection it becomes 

 a difficult one to exterminate. No means of trapping the flies 

 are known, and the only apparent remedy has been the heroic 

 one of cutting off and destroying all portions of the plants sus- 

 pected of being infested. The young pseudo-bulbs usually 

 become somewhat abnormally swollen if the maggots are at 

 work within, although the indication is not always a certain 

 one. To cut these young shoots off means the loss of flow- 

 ers for a year. 



It has been suggested that the larvae could be killed in their 

 burrows by prodding the infested shoots with a triangular dis- 



