208 



The Dictionary of Gardening, 



Potato — continued. 

 is in the soil, it should be either removed or counter- 

 acted. Potatoes should not be grown in soil known to 

 give rise to scabbing. 



Insect Pests. There are no insects, in the British 

 Islands, absolutely confined to the Potato as their food ; 

 but several occasionally devour this, as well as other cul- 

 tivated plants.* To begin with those that eat the roots 

 and tubers. Amongst the worst are the larva; of several 



Fig. 258. Skip.iack, or Click Beetle— o, Line showing 

 the natural length. 



kinds of Skipjack Beetles (see Figs. 258 and 259), 

 which bore holes in the tubers, to which they are very 

 partial {see 'Wire'worms). The larva3 of Cockchafers 

 (Melolonthn viilriarii!) and Mole Crickets (Gryllotdlpa 

 vulgaris) also gnaw them, and the roots at times (see 

 Cockchafer and Mole Cricket). 

 The larva' of certain Kvrfiiw, or Night 

 Motlis {see Noctua and Turnip 

 Moth), are sometimes very destruc- 

 tive to the tubers, but do compara- 

 tively little harm to the other 

 subterranean organs, since, as a rule, 

 they do not feed at the season of 

 growth of Potato-plants. Among the 

 most harmful are the Heart-and-Dart 

 Moth {Affi-ofiy exclawatio}iis), the 

 Turnip Moth (.4. sef/etiim). and nearly- 

 allied species. The larva; of Crane 

 Flies {Tipula olevacea and allies), 

 commonly known as the Grub, or 

 as Leather Jackets, because of the 

 toughness of their skins {see Crane 

 Ply), frequently injure the roots of 

 growing Potatoes, and may also feed 

 on the young tubers, though most de- 

 structive to grasses. Many kinds 

 of small Dipfenf live, as larvte, in 

 decaying Potato tubers, and Curtis, 

 in his '• Farm Insects," has recorded 

 ten species reared by himself from 

 this food ; but there is no evidence 

 to show that they injure healthy 

 tubers. Millipedes, including Poly- 



desmits compJanaftts, and one or two species of Jnhis 

 {see Millipedes and Myriapoda), are often found 

 feeding in the tubers, but they hardly seem to bore 

 into them if quite healthy, and, in general, appear to 

 take advantage of holes scooped out by the larvae 

 already mentioned, or to bore into tubers which are 

 softened by disease. Centipedes also {see Myriapoda) 

 are often found in holes in the tubers, but they are all 



Fig. 259. Wireworm, or Larva of Skipjack Beetle. 



carnivorous, and probably assist in reducing the number 

 of destructive larva;. Last of the animals that destroy 

 the tubers, must be mentioned the various kinds of Slugs, 

 which eat large holes in them, and continue to feed in 

 these till, occasionally, there is little left of the smaller 

 tubers {see Sing's). Slugs do not seem to do much 

 harm to the green parts of Potato-plants. 



The green stems and the leaves are not, as a rule, 

 liable to severe insect attacks with us, though in North 



Potato — continued. 

 America they suffer much damage from this cause. The 

 more injurious of these American insects will be here 

 briefly referred to after mention has been made of such 

 as have been observed in Britain. 



Curtis records finding a beetle {Marrociiemn exolefa), 

 allied to the Turnip Flea, feeding on the leaves of 

 Potatoes, and .still more abundantly on the Bitter-sweet 

 Solanum Dulcamara). The beetle has the head black, 

 the thorax deep ochreous. the elytra pale ochreous, 

 except a pitchy line down the suture, and the limbs 

 pale. It is from rVin. to Jin. long. These pests can 

 scarcely be ranked as a serious danger to the Potato 

 crop, but, should they become dangerous to it, they may 

 be reduced in numbers by the same methods as are 

 employed against the Turnip Flea (which see). 



Of moths, few live, in the larval state, on Potato 

 leaves ; but one species is almost restricted to this 

 plant — the Death's Head Hawk Moth {AcJierontia Atro- 

 pos). This moth (see Fig. 260) is one of the largest 

 and handsomest of our native species. The appear- 

 ance, form, and markings, are shown in the woodcut ; 

 but the spread of wings may be 5in. The fore wings 



Fig. 260. Death's Head Hawk IIoth. 



are a 6ne brown, with darker and paler markings, and 

 a conspicuous yellow dot in the centre. The hind 

 wings are orange-yellow, with two dark bands. The 

 body is yellow and brown, with six black cross bands on 

 the abdomen, and a row of six bluish spots down the 

 middle of the back. The thorax bears, between the fore 

 wings, a large mark, like a skull, or "Death's head," 

 whence the popular name. Because of this mark, also, 

 the insect is much dreaded, in various parts of Europe, 

 by superstitious rustics and others, as ill-omened; and 

 this impression is deepened by the power (very rare 

 among moths) of emitting a sharp squeak when 

 handled. The larva and pupa can also emit peculiar 

 sounds. The larva feeds now chiefly on Potatoes ; though 

 it has also been found on the Jasmine, the Deadly 

 Nightshade {.itropa Belladonna), and the Tea - tree 

 {Lycium barbarum). It reaches a very large size, tapering 

 a little towards the head, but ending abruptly behind, 

 where it bears a small horn, very rough, yellowish, 

 and bent downwards, but turned up at the tip. The 

 creature is smooth, and is usually pale yellow on the 

 back, and green near the head and along the lower 

 part of the sides. There are seven oblique, violet or 



