SPAN-WORMS. 



begun. Their general time of rising is in the 

 spring, beginning about the middle of March, 

 but sometimes before, and sometimes after this 

 time ; and they continue to come forth for the 

 space of about 3 weeks. It has been observed 

 that there are more females than males among 

 those that appear in the autumn and winter, 

 and that the males are most abundant in the 

 spring. The sluggish females instinctively 

 make their way towards the nearest trees, and 

 creep slowly up their trunks. In a few days 

 afterwards they are followed by the winged and 

 active males, which flutter about and accom- 

 pany them in their ascent, during which the 

 insects pair. Soon after this, the females lay 

 their eggs upon the branches of the trees, 

 placing them on their ends, close together, in 

 rows, forming clusters of from 60 to 100 eggs 

 or more, which is the number usually laid by 

 each female. The eggs are glued to each other, 

 and to the bark, by a grayish varnish, which is 

 impervious to water; and the clusters are thus 

 securely fastened in the forks of the small 

 branches, or close to the young twigs and buds. 

 Immediately after the insects have thus pro- 

 vided for a succession of their kind, they begin 

 to languish, and soon die. The eggs are usually 

 hatched between the first and the middle of 

 May, or about the time that the red currant is 

 in blossom, and the young leaves of the apple 

 tree begin to start from the bud and grow. The 

 little canker-worms, upon making their escape 

 from the eggs, gather upon the tender leaves, 

 and, on the occurrence of cold and wet weather, 

 creep for shelter into the bosom of the bud, or 

 into the flowers, when the latter appear. Where 

 these insects prevail, they are most abundant 

 on apple and elm trees ; but cherry, plum, and 

 lime trees, and some other cultivated and na- 

 tive trees, as well as many shrubs, often suffer 

 severely from their voracity. The leaves first 

 attacked will be found pierced with small holes ; 

 these become larger and more irregular when 

 the canker-worms increase in size ; and, at 

 last, the latter eat nearly all the pulpy parts of 

 the leaves, leaving little more than the midrib 

 and veins. A very great difference of colour 

 is observable .among canker-worms of different 

 ages, and even among those of the same age 

 and size. It is possible that some of these va- 

 riations may arise from a difference of species; 

 but it is also true that the same species varies 

 much in colour. When very young, they have 

 2 minute warts on the top of the last ring ; and 

 they are then generally of a blackish or dusky 

 brown colour, with a yellowish stripe on each 

 side of the 'body; there are 2 whitish bands 

 across the head ; and the belly is also whitish. 

 When fully grown, these individuals become 

 ash-coloured on the back, and black on the 

 sides, below which the pale yellowish line 

 remains. When fully grown and well fed, 

 they measure nearly or quite 1 inch in length. 

 They leave off eating when about 4 weeks old, 

 and begin to quit the trees ; some creep down 

 by the trunk, but great numbers let themselves 

 down by their threads from the branches, their 

 instincts prompting them to get to the ground 

 by the most direct and easiest course. When 

 thus descending, and suspended in great num- 

 bers under the limbs of trees overhanging the 

 1004 



SPAN-WORMS. 



road, they are often swept off by passing car- 

 riages, and are thus conveyed to other places. 

 After reaching the ground, they immediately 

 burrow in the earth, to the depth of from 2 to 6 

 inches, unless prevented by weakness or the 

 nature of the soil. In the latter case, they die, 

 or undergo their transformation on the surface. 

 In the former, they make little cavities or cells 

 in the ground, by turning round repeatedly and 

 fastening the loose grains of earth about them 

 with a few silken threads. Within 24 hours 

 afterwards, they are changed to chrysalids in 

 their cells. The chrysalis is of a light brown 

 colour, and varies in size according to the sex 

 of the insect contained in it ; that of the female 

 being the largest, and being destitute of a 

 covering for wings, which is found in the chry- 

 salis of the males. The occurrence of mild 

 weather after a severe frost stimulates some of 

 these insects to burst their chrysalis skins and 

 come forth in the perfect state ; and this last 

 transformation, as before stated, may take 

 place in the autumn, or in the course of the 

 winter, as well as in the spring; it is also re- 

 tarded, in some individuals, for a year or more 

 beyond the usual time. They come out of the 

 ground mostly in the night, when they may be 

 seen struggling through the grass as far as the 

 limbs extend from the body of the trees under 

 which they had been buried. As the females 

 are destitute of wings, they are not able to 

 wander far from the trees upon which they had 

 lived in the caterpillar state. Canker-worms 

 are therefore naturally confined to a very 

 limited space, from which they spread year 

 after year. Accident, however, will often carry 

 them far from their native haunts, and in this 

 way, probably, they have extended to places 

 remote from each other. Where they have 

 become established, and have been neglected, 

 their ravages are often very great. In the early 

 part of the season the canker-worms do not 

 attract much attention ; but in New England it 

 is in June, when they become extremely vora- 

 cious, that the mischief they have done is ren- 

 dered apparent, when we have before us the 

 melancholy sight of the foliage of our fruit 

 trees and of our noble elms reduced to withered 

 and lifeless shreds, and whole orchards look- 

 ing as if they had been suddenly scorched 

 Avith fire. 



In order to protect our trees from the ravages 

 of canker-worms, where these looping spoilers 

 abound, it should be our aim, if possible, to 

 prevent the wingless females from ascending 

 the trees to deposit their eggs. This can be 

 done by the application of tar around the body 

 of the tree, either directly on the bark, as has 

 been the most common practice, or, what is 

 better, over a broad belt of clay-mortar, or on 

 strips of old canvass or of strong paper, from 

 6 to 12 inches wide, fastened around the trunk 

 with strings. The tar must be applied as early 

 as the 1st of November, and perhaps in Octo- 

 ber, and it should be renewed daily as long as 

 the insects continue rising; after which the 

 bands may be removed, and the tar should be 

 entirely scraped from the bark. When all this 

 has been properly and seasonably done, it has 

 proved effectual. The time, labour, and ex- 

 pense attending the use of tar, and the injury 



