Morok 5, 1974. J 



JOURNAIi OP HORTICULTORE MD COTTAGE GARDENER. 



201 



to the window, or a cool greenhouse, where the development 

 of the blossoms will proceed more favourably than when fully 

 exposed. In the southern counties, in favourable localities and 

 in suitable soils, it may bo planted-out after danger of frost is 

 over ; but the corms should be repotted in autumn, as it is 

 incapable of resisting severe frost. 



Tritonia aurea may be increased by seed, which is produced 

 by the strongest flower scapes, if the plants are continued in 

 growth after flowering ; and the seed should be sown as soon 

 as gathered, the young plants being carefully preserved from 

 frost the foUowiug winter. It is worthy of remark in con- 

 nection with the growth of this plant, that the new corm 

 annually produced is found at a distance varying from one to 

 several inches from that of the previous year, with which it is 

 connected by a stout fibre. Whether the older corms perform 

 any usefuJ function is uncertain, but they never flower but 

 once, though often remaining undecayed for years. As the 

 bulbs of some species of Tritonia may be preserved in a dry 

 state for weeks, it is necessary to point out that in the case of 

 T. aurea the drying-off process must not be attempted. When 

 the foliage withers water may be partially withhold, but the 

 soil must on no account be permitted to become (luite dry. 



The blossoms of this plant when dried, and afterwards moist- 

 ened with warm water, give out a strong odour of saffron, 

 which circumstance has induced Dr. Planchon to constitute it 

 a new genus under the name of Crocosma, by which it some- 

 times occurs in catalogues. — ()('. TJiompsoii's EnpUsli Flower 

 Garden, Kcvised hij the Author.) 



A NEW ENEMY OF THE POTATO. 



1 WISH to say a few words about an enemy which threatens 

 to lay waste one of Europe's most valued esculents, the Potato. 

 For a long time North America has had to contend against two 

 foes, which devoured the early shoots and leaves of the Potato, 

 and thus destroyed the hopes of the farmer and gardener. 

 These were beetles belonging to the same family as the Blister- 

 fly, and named Lytta atrata for vittata) and Cantharis viniaria. 

 They can bo kept within bounds ; but of late a third beetle 

 has appeared among us, which really threatens to drive the 

 Potato out of cultivation altogether. It bears the name of 

 the Colorado Potato-beetle (Doryphora decem-punctata) ; and 

 should it once reach the Atlantic coast, and be carried unob- 

 served across the ocean, then — woe to the Potato-grower of the 

 old country ! 



A man must witness the myriad legions of this insect, and 

 the ravages of its never- tiring larvte, in order to form an idea 

 of the terrible danger with which Europe is threatened. For 

 myself, judging from the tenacity of hfe exhibited both in its 

 larval and perfect condition, I have not a doubt that it will 

 soon overstep the bounds of North America, and make a home 

 for itself in other lands. 



Its true domicile is in the Rocky Mountains, where it feeds 

 on a species of wild Potato, Solanum rostratum (or carolinianie). 

 No sooner, however, had the edible Potato (Solanum tuber- 

 osum) been planted by settlers at the foot of these mountains, 

 than Doryphora attacked it greedily ; the more largely its cul- 

 tivation extended westward, the faster did its insect foe travel 

 in an easterly direction, and scatter itself over the land. In 

 the year 18"i'J it was located one hundred miles west of Omaha 

 city, in Nebraska; in 1851 it showed itself in Iowa ; in 18(J5, 

 not only had it begun to devastate Missouri, but it had crossed 

 the Mississippi in Illinois, everywhere leaving behind it flourish- 

 ing colonies. In 18(jS Indiana was visited ; in 1870 Ohio and 

 the confines of Canada were reached, also portions of Penn- 

 sylvania and New York ; and its entrance into Massachusetts 

 was notified. During the year 1871 a great army of these 

 beetles covered the river Detroit in Michigan, crossed Lake 

 Eric on floating leaves and similar convenient rafts, and in a 

 very short time took possession of the country between St. 

 Clair and Niagara rivers. Having got thus far, in spite of aU 

 efforts to stay then' progress, there is every reason to believe 

 that before long we shall hear of them as swarming in the 

 streets of New York and Boston (as they already swarm in the 

 city of St. Louis), and then their passage across the Atlantic 

 is a mere matter of time. Sloreover, the beetle in its different 

 stages is so entirely unaffected by the extremes of heat and 

 cold, of wet and dry, which it has met with here, that I have 

 no doubt it will care as Utile for the changes of climate which 

 occur in the temperate zone of Europe, and, once settled, will 

 quickly become naturalised. 



The devastations of the Colorado beetle are all the greater 



from the fact of its propagating itself with extraordinary 

 rapidity, several broods following each other in the course of 

 the year. The first batch of infant larva; appears towards the 

 end of May, or, if the weather be mUd, of April. In fact, 

 scarcely has the Potato plant shown itself above the ground, 

 before the insect, which has been hybernating during the 

 winter, also wakes to life. The female loses no time in de- 

 positing from seven hundred to twelve hundred eggs, in clusters 

 of twelve or thirteen, on the under side of a leaf. Within five 

 or six days, according to the state of the weather, the larvae 

 escape from the egg and begin their work of devastation, 

 which goes on for some seventeen days, when the little creatures 

 retire below the soil, in order to undergo the pupal condition. 

 After a delay of ten or fourteen days the perfect insect comes 

 into being, and the business of egg-laying commences anew. 

 In this way, according to recent observations, three broods 

 follow each other ; the last, as just stated, wintering below the 

 surface of the ground. No description can do justice to the 

 marvellous voracity of this insect, especially in its larval state. 

 When once a field of Potatoes has been attacked all hope of a 

 harvest must be given up ; in a very few days it is changed 

 into an arid waste — a mere mass of dried-up stalks. 



Fi'j. 1.— Coloraao Potato beetle iu different stages, from egg to iierfect iuoecls. 



At one time the cultivator indulged in the vain hope that 

 Doryphora was a mere passer-by, that he would do his worst 

 and then move on, without becoming a permanent nuisance. 

 Others, again, fancied that a hot summer and autumn, followed 

 by a long drought in the ensuing year, tended to diminish its 

 numbers. But it has been proved incontestably that tho 

 diminution was only due to the circumstance of many of the 

 larv;e perishing, through being unable to enter the ground 

 hardened and baked by the great heat; plenty were left to 

 continue the breed. 



Of the many nostrums that have been employed for the 

 destruction of this beetle, one only has shown itself to be of any 

 value. I mean, dusting the plants with the highly poisonous 

 substance Paris green— a compound of arsenic and oxide of 

 copper. However, setting aside the dangers of inhaling this 

 deadly mixture whUo spreading it over the fields, there is tho 

 additional peril of impregnating tho soil with it— a peril which 

 experiments carried out at Washington have shown to bo well 

 foimded. There remains, therefore, only tho plan of hand- 

 picking, day after day, the eggs, larv;c, and beetle ; but even 



Fig. -2 a, Cojurado beetle, 'i, Foot of ditlo. r, ruiiaoXt.ilio. (/, Wing- 

 case, enlarged. 



this operation re(iuires considerable care, for the juice of the 

 crushed insect and its larvic produces bladders and blisters 



