162 



THE LANCASTER FARMER 



[November, 



The Sack-Worm. 

 ( Ths/ridopteryx ephemarre/ormis.) 



The "Sack-worm," alias "Bag-worm," 

 "Basket-worm," "Drop-worm," and other 

 local names, has been numerous and destruc- 

 tive the past season, and especially so iu some 

 of the Southern States, and 7nost especially so, 

 about Atalanta, in Georgia; at least, a special 

 wail came up from that locality, both by pub- 

 lic and by private communication, as may be 

 perceived on page 132 ^September No.) of the 

 present volume of the Farmer. 



The first specimen of this insect that came 

 under our observation (to the best of our re- 

 collection) we found on a locust tree, about 

 1844 in York county, opposite Marietta. 

 Nothing come of it ; for, it either died in its 

 sack, or had issued from it, before it came 

 into our possession. About a year thereafter, 

 a short paragraph cut out of a Philadelphia 

 paper, was given us, the purport of which was 

 that Mr. Peal, of Philadelphia, had found 

 two of these sacks pending from a branch of 

 a tree on the banks of the Wissaliickon, in the 

 year 1813 or 1814 ; from the brief description 

 of which we concluded they were the same as 

 the one we found in York county. We did 

 not see or hear tell of anotlier specimen, until 

 we removed to Lancaster city in 1848, where 

 we met them in great abundance during the 

 years 1849, 18.50 and 18.51, when we com- 

 menced a series of observations on them, and 

 traced them through all their transformations, 

 from the ova to the imago. These observa- 

 tions we committed to paper, but the manu- 

 script remained in our possession until the 

 summer of 1854, when, at the request of the 

 publislier of the Pennsylvania Farm Journal, 

 they were published in that paper under tlie 

 provisional name of Oiketicus pensylvaniciis. 

 About the same period an article by Dr. Har- 

 ris, on the same insect, was published in, we 

 think, the Rochester Horticulturist, Dr. H. 

 naming it — from specimens sent to him — 

 Oiketicus coniforum, because the specimens 

 had been taken from a pine tree. It appears 

 however that it had been previously described, 

 and named as above. So much has been pub- 

 lished in reference to this insect that it is 

 hardly necessary to say anything, eitlier de- 

 scription, or on the manner of destroying it. 

 Its operations are so conspicuous, and it is so 

 accessible withal, that if any one suffers by it, 

 it must be purely their own fault. 



What our special purpose is on this occa- 

 sion is to refer to the fact that this insect is 

 preyed upon by several parasites, which, if 

 proportioned to the number sent us, are suf- 

 ficient to keep it in reasonable check. We 

 placed four of the Southern specimens in a 

 glass jar, and it was wonderful to see how 

 deftly they could crawl up its sides, drawing 

 their sacks after them, and mooring them at 

 auy time or place in a moment, and retreat- 

 ing witliin them. Seeing that they would not 

 feed we set the jar aside, and did not examine 

 it again until the 1st of October, when we 

 found three empty brown pupa-skins and 

 three Tachina flies, something larger than the 

 domestic house-fly. On opening the sacks we 

 found in one a male pupa, and in tlie other 

 three the shriveled bodies of tire partially con- 

 sumed larvft. Here were three out of the four 

 destroyed by parasites. We are not prepared 

 to say that three out of four 2)er see would be 



subject to parasitic infestation ; but, on the 

 otlier hand, it might possibly be a greater per- 

 centage. 



Now, the wonder is liow a parasite could 

 approach this insect at all, much less succeed in 

 depositing an egg in or on its body. From the 

 period when the young larva is excluded until 

 its evolution as a male moth (the female 

 never leaving the follicle or sack) tliese larvse 

 are enveloped in a tough silky sack, covered 

 on the outside with shreds or dry leaves, and 

 so well protected that we think no bird can 

 dislodge theni— at least, we have seen chick- 

 ens attempt it and abandon it with disgust. 



But it appears they are not inaccessible to 

 parasites. As early as 18.59 or 60 we opened 

 one of these sacks and found the inner cavity 

 filled with white silky coccoons, numbering a 

 half dozen or more. These, in tlie multiplicity 

 of other more pressing occupations were set 

 aside, and when subsequently examined the 

 insects had escaped, if they had not already 

 escaped before we discovered their coccoons. 

 This is, perhaps, the Hymenopterous insect 

 found under similar circumstances, and 

 described by Prof. Riley as Hemileles thyridop- 

 teryx, p. 1.50, First Report on the Noxious In- 

 sects of Missouri. 



Mr. Glover, in his unpublished plates, 

 figured Cryptus inquisitor, of Say, as parasitic 

 on the sack-worm. Say describes several 

 species of cryptus perhaps without knowing 

 tlieir parasitic habits. 



The parasites described by Say and Riley, 

 are however Hymenopterous insects ; but the 

 one we refer to is Dipterous, and to illustrate 

 that they could not have been introduced 

 into the jar extraneously, one of the pupa 

 shells was found within the unopened sack, 

 the fly of which escaped no doubt through an 

 elastic, or collapsed apercure, through which 

 the young sack-worms escape, at the lower 

 end of the sack. This fly is pretty large in 

 proportion to its host; and therefore a sack- 

 worm may only afford sustenance to one 

 parasite. Very little more than the heads and 

 two of the anterior segments of the sack- 

 worm remained unconsumed. In a practical 

 sense, tliat is as much as can be desired. 

 Tlie destruction of one female sack-worm 

 defeats the possibility of a subsequent brood 

 of two or three hundred. The benefits of 

 these parasites are, therefore, very evident 

 because nothing but these, and hand-picking 

 can reach them. Tlie application of a liquid 

 or a powder would be of little avail. These 

 sacks hang upon the trees all winter, and no 

 matter how cold and wet, and freezing it is, 

 inside of the sack it is "dry as powder," and 

 the eggs, or embryotic sack-worms, are be- 

 yond the evil influences of " wind and 

 weather." Our limited entomological litera- 

 ture yields no instance of tachinic infestation 

 (or we have overlooked it) so far as it relates 

 to the sack-worm, and from a peculiar cliarac- 

 teristic of these flies — tlieir rapid or swift 

 flight — they would seem to possess the neces- 

 sary activity to enable them to oviposit in, or 

 on the body of a sack-worm ; for in endeavor- 

 ing to discover liow they managed to draw 

 themselves perpendicularly over the side of a 

 glass jar, only the sounds caused by our 

 breathing would cause them instantly to draw 

 in their bodies, and collapse the upper end of 

 the sack. Under such circumstances, as we 



have before intimated, the sack would not 

 drop to the bottom of the jar, but would re- 

 main fixed until the worm would project its 

 body again. The secret is, they spin a very 

 fine, strong, elastic and adhesive silk cord, 

 which is constantly in communication with 

 the mouth-parts, and this seems to immedi- 

 ately adhere to any substance which the in- 

 sect touches — indeed, in traveling over a ver- 

 ticle glass surface, the head seems to be more 

 employed than the feet. This insect then, 

 which has heretofore been regarded, to some 

 extent, as proof against parasitic infestation, 

 is as likely to become, tachinized at least, as 

 any other insect. 



According to observations made by Harris, 

 Walsh, Riley, Kirk and others, there are 

 some fifteen or sixteen species of Tachnib^e 

 that are parasitic on Army-worms, Canker- 

 worms, Cotton-worms, Maple-worms, Leaf- 

 crumplers, the larvse of Attacics cecropia. A. 

 polyphemus, Dryocampa rubicunda, and the 

 Colorado potato beetle. Namely, seven of 

 Tachina, six of Exorista, and one or more of 

 Lydella ; and we think that two more may be 

 added, namely, those of the Thyridopteryx 

 and the Empretia. Of these genra Curtis has 

 catalogued twelve species of Exorista, eight 

 of Lydella, and four of Tachina ; and many 

 other allied genera and species. 



Whether the two individuals to which we 

 refer in this paper are new species, or whether 

 they are among those that have already been 

 described, is a matter left to future determi- 

 nation ; not being essential to the economic 

 discussion of the question. Our object is 

 merely to illutrate that insect paracitism ex- 

 ists more widely than is usually suspected, 

 that it is becoming yearly more manifest, and 

 that it exercises a greater influence over the 

 development of the insect world than the 

 ordinary observer ever dreams of. Suppose 

 that the Bag-worm and the Saddle-back were 

 to become as numerous and wide-spread as 

 the Bocky Mountain Locust and the Western 

 Chinch-bug ; what, except hand-picking, could 

 more effectually exterminate them than para- 

 sitic infestation ? True, the Saddle-back 

 moves so very slowly that it might easily be 

 destroyed by poisonous compounds, but no- 

 body would care to remove it with the naked 

 hand, seeing that they might suffer more than 

 they would by handling poison. Here then 

 the ubiquitous parasite comes in most appro- 

 priately as the friend of the human family, 

 for the preservation of tlie plant world effects 

 the interests of the consumer as well as the 

 producer. 



Saddle-Back Moth. 

 (Eniprelttt stimuhi.) 



We never knew the larva of this insect to 

 be more abundant than it has been the pres- 

 ent season (August and September, 1884) ; 

 nor did we ever before meet with so many 

 people who had seen it for the first time, and 

 who were more completely ignorant of its 

 previous existence. "Certainly something 

 new " was reiterated by every one who brought 

 us specimens. Neither did it ever before be- 

 come so manifest to us what a destructive 

 scourge this insect might become, if it ever ap- 

 proximated in number, tlie "Army-worm," 

 " Canker-worm," Cabbage- worm " or "Colo- 

 rado Potato Beetle." Apple, pear, quince, 

 plum, lilac, rose, elm, linden, corn, plantain. 



