150 THIRD ANNUAL EXPORT OF 



Our Tachina-flies generally very closely resemble each other, and 

 very little attention has been paid to them in this country. The present 

 species seems to be new to science, but I forbear to describe it for the 

 simple reason that it varies so much in itself and so closely resembles 

 many others, that it would be n?xt to impossible to characterize it 

 sufficiently. It may be provisionally known, for purposes of reference, 

 as the Archippus Tachina-fly— Tachina* arc/nppivora. It may be at 

 once distinguished from the two ilies described in my second Keport 

 (p. 51), and which attack the true Army-worm, not only by the differ- 

 ent form and smaller size, but by being of a paler gray, and by lacking 

 the reddish or yellowish tail. The eyes are perfectly smooth. An 

 interesting fact connected with this fly is that it likewise attacked 

 the Fall Army-worm (as already mentioned on page 116, note,) 

 which was so abundant at the same time of year. I have also bred it 

 undescribed cut worm. 



The Tachinarics can only be satisfactorily studied in connection with their habits, and even 

 then they must prove a most difficult Division to work up. The species are very apt to grease in the 

 cabinet and where they do not grease, the colors, especially of the face, lose their brilliancy. I am 

 satisfied that the same species often attacks indifferently many widely distinct larva; and that there 

 are, in consequence, entomophagic varieties. I have a score of different lots, bred from as many 

 distinct species of Lepidopterous and even Coleopterous larva); and the individuals of each lot, 

 often bred from a solitary specimen of some particular species of larva, differ more among them- 

 selves than from individuals of some other lot, bred from a distinct species of larva. Indeed, 

 unless there are striking characters, it would be folly for any but the specialist to attempt to 

 describe them. These Tachina-fiies, indeed, form such an extensive Division that in order to facil- 

 itate study, authors have inclined to erect genera upon characters most trivial and such as would 

 certainly not be looked upon as of more than specific value in other groups. Sixteen specimens 

 bred from Danais archippus vary from 0.1S — 0.30 inch in length and from 0.33 — 0.60 inch in ex- 

 panse : some have a rufous spot on the side of the second abdominal joint, while others show no 

 signs of any such spot. From among them two somewhat distinct forms occur in about equal 

 numbers. In the one, which is on an average the largest, the abdomen is rather broader, and when 

 dry shrinks so as to become flat, while the antenna? have the third joint from four to five times as 

 long as the second. In the other the abdomen is rather narrower, remains more cylindrical when 

 dry, and the antenna? have the third joint from five to six times as long as the second. These dif- 

 ferences are, I believe, sufficient to cause the specialist to make distinct species or even genera; 

 but as the same two forms occur in those bred from other species of larva;, and as all the other 



coarctate pupa? was so regularly and smoothly opened by the nascent fly ; but am now satisfied 

 from observations made on this particular species, that it is previously prepared by the larva while 

 contracting, in the manner described above. This will be more especially the case where the con- 

 tracted skin is thick as in Cuterebra, (Estrus, etc., while in those where the skin is thin and delicate 

 as in Anlhomyia and many of the smaller Muscidce, the habit probably does not obtain, as the fly 

 can crowd itself out, and the opening is quite irregular, sometimes transverse, at others forming a 

 simple longitudinal slit. I have witnessed the same wonderful forethought in the larva of Chry- 

 sopa, after spinning its small cocoon. In this case the sharp sickle-like jaws of the larva enable it 

 to cut very finely and smoothly, and the edge of the severed parts show plainly, under the lens, a slight 

 discoloration. The circle inscribed is often, but not always, slightly spiral so that when pushed 

 open the lid hangs as on a hinge. The same habit no doubt prevails in the Lepidopterous genus 

 Limacodes and its allies ; for 1 have experimentally proved, by opening several cocoons of Callo- 

 chlora viridis, Reakirt, both while the inmate was yet in the larva or pupa state, that the lid opens 

 with the slightest pressure, and just as regularly as if pushed from within. There is, however, a 

 marked difference in the working in these last two cases and that of our Dipterous larva?. The 

 former enclose themselves in cocoons, in which they have abundant room to turn round and par- 

 tially cut their lid, while -the Tachina larva performs the work on its own skin while it is harden- 

 ing and before it has become separated from the transforming body within. 



* I forwarded specimens of this fly to Dr. LeBaron, the State Entomologist of Illinois, who is 

 better posted as to the minute generic differences between these flies, than any one else in the West, 

 and he refers it to the genus Masicera, Macq., in speaking of which Macquart says : "they are the 

 only Tachina which have the third joint of the antenna? very long without at the same time having 

 tlic front very prominent." This and other minor genera of Macquart and Meigen have been dis- 

 carded by some modern authors, such as Walker and Zetterstedt, and referred to Tachina. 



