324 



THE FARMERS' REGISTER. 



into Spain, at his own expense, for the purpose of 

 inspecting the geological occurrence ol'lhis mine- 

 ral in that country. 



GEOMETERS, CANKER-WORMS, PLANT LICE. 



(From Harris's Report on the Insects of Massachusetts.) 



The caterpillars of the GeojnetrcB ol LinnsBus, 

 earth- measurers, as the term implies, or geome- 

 ters, span-worms, and loopeis, have received these 

 eeveral names Irom their peculiar manner ol 

 moving, in which they seem to measure or span 

 over the ground, step by step, as they proceed. 

 Most of these caterpillars have only ten legs; 

 namely, six, which are jointed and tapering 

 under the lore part of the body, and lour fleshy 

 proplegs, at the hinder extremiiy; the three in- 

 termediate pairs of proplegs being wanting. 

 Consequcnily, in creeping, they arch up the back 

 while they bring lorward the hinder part of the 

 body, and then resting on their hind legs, stretch 

 out (0 their lull length, in a straight line, before 

 taking another step with iheir hind legs. Some 

 of the geometers have twelve or Jburteen legs ; 

 but the additional proplegs are so short that the 

 caterpillars cannot use them in creeping, and their 

 motions are the same as those that have only ten 

 legs. Some caterpillars wiih fourteen legs, and 

 wanting only the terminal pair of proplegs, are 

 placed in this tribe on account of the resemblance 

 of their moths, to those of the true geometers. 

 The latter live on trees and bushes, and most ol 

 them undergo their transformations upon or in 

 the ground, to reach which, by travelling along 

 the branches and down the siem, would be a 

 long and tedious journey to them, on account of 

 the deficiency of iheir legs, and the slowness of 

 their gait. But they arc not reduced lo this ne- 

 cessity ; for ihey have the power of letting them- 

 selves down from any height, by means of a silken 

 thread, wliich they spin from their mouths while 

 falling. Whenever they are disturbed, ihey make 

 use of this faculty, drop suddenly, and hang sus- 

 pended, I ill the danger is past, alter which they 

 climb up again by the same thread'. In order to 

 do this, the sp;in-worm bends back its head and 

 catches hold of the thread above its head with 

 one of (he legs of the iliird segment, then raisiuir 

 its head it seizes the thread with its jaws and fore 

 legs, and, by repealing the same operations with 

 tolerable rapidity, it soon reaches its firmer ela- 

 tion on the tree. These span-worms are naked, 

 or only thinly covered with very short down ; 

 they are mostly smooth, but sometimes have 

 warls or irregular projections on their backs. 

 They change their color usually as they grow 

 older, and sometiiTies of one nnilbrm color, nearly 

 reeembling the bark of the plants on which they 

 are found. When not eating, many of them rest 

 on the two hindmost pairs of legs against the 

 Gido of a branch, with the body extended from 

 the branch, so that they might be mistaken for a 

 twig of the tree; and in this position they will 

 often remain (or hours together. When about to 

 transform, most of these insects descend from the 

 plants on which they live, and either bury them- 

 selves in the ground, or conceal themselves on 

 the surface, under a slight covering of leaves fas- 

 tened together with silken threada. Some make 



more regular cocoons, which, however, are very 

 thin, and generally more or less covered on the 

 outside wiih leaves. The cocoons of the Ku- 

 ropean-iailed geometer ( Ourapteryx snmbucaria,') 

 which lives on the elder, and of our chain-dotted 

 geometer (Geomclra catenaria,) which is Ibund 

 on the wood-wax, are made with regular meshes, 

 like net-work, ihrout'h which the insects may be 

 seen. A very few of the span-worms fasten 

 themselves to the stems of plants, and are changed 

 to chrysalids, which hang suspended, without the 

 protection ol' any outer coverinir. 



In their perlected state, these insects are mostly 

 slender-bodied moihs, with tapering antennae, 

 which are ofien feathered in the males. Their 

 liselers are short and slender ; the tongue is short 

 and weak ; the thorax is not cresied ; the wings 

 are large, thin, and delicate — sometimes angular, 

 and often marked with one or two dark-colored 

 oblique bands. They generally rest with the 

 wings slightly iticlined and almost horizontal ; 

 some with them extended, and others with the 

 hind wings covered by the upper pair. A very 

 lew carry their wings like the skippers. Some of 

 the lemales are without wings, and are distin- 

 guished also by the oval and robust form of their 

 bodies. These moths are most active in the 

 night ; but some of them may be seen flying in 

 thickets during the day time. They are very 

 short-lived, and die soon after their eggs are laid. 



Those kmds whereof the females are wingless, 

 or have only very short, scale-like wings and naked 

 anteniice, while I he males have large, entire wings, 

 and feathers or downy antennas, seem to form a 

 di.otincl group, which may be named hybernians 

 (IJybcrniad<B,) liom the principal genus included 

 therein. The caterpillars have only ten legs, six 

 belbre and four behind ; and they undergo their 

 transformations in the ground. The insects called 

 canker-worms, in this country, are of this kind. 

 The moths, from which they are produced, belong 

 lo the rrenus jlnisoptcryx, (literally unequal wing,) 

 so named because in some species the wings in the 

 two sexes are very unequal in size, and in others 

 the females are winalese. In the late Professor 

 Peck's " Natural History of the Canker-worm," 

 which was p\il)lished among the papers of the 

 Massachusetts Society for promoting Agriculture, 

 and obtained a prize from the society, this insect is 

 called PhaJa'na rernnla, on account ofits common 

 appearance in the spring, and also to distinifuish it 

 from the winter moth {Pluilana or Chchnatobia 

 hrumala) of lilurope. In the male canker-worm 

 moth tlie antenufij have a very narrow, and al- 

 most downy edging, on each side, hardly to be 

 seen with the naked eye. The feelers are minute, 

 and do not extend beyond the mouth. The 

 tongue is not visible. The wings are large, very 

 thin and silky ; and, when the insect is at rest, 

 the fore wings are turned back, entirely cover the 

 hind wings, and overlap on their inner edges. 

 The fore wings are ash-colored, with a distinct 

 whitish spot on the front edge, near the tip ; they 

 are crossed by twojatrged, whitish bands, along 

 the sides of which there are eeveral blackish dots ; 

 the outermost band has an angle near the front 

 edge, within which there is a short, faint, blackish 

 line ; and there is a row of black dots along the 

 outer margin, close to the fringe. The hind 

 wings arc pale ash-colored, with a faint blackish 

 dot near the middle. The wings expand about 



