AN EGG-PARASITE OF THE CURRANT SAW-FLY. 217 



haps also in Hepialus, the pupae of which (unknown to me) are character- 

 ized as very similar to those of Cossiis. 



Another interesting fact connected with the armature of Cossiis is that 

 the form, size and position of the teeth vary to so great an extent in the 

 different species, and show such distinctive characters, as to afford excel- 

 lent specific features.* I would not hesitate to pronounce upon specific 

 identity, upon an examination and comparison of the pupal armature 

 alone. 



\_Fi-oiit Psyche, May-June, 1883, iv, y>/. 48-51.] 



ON AN EGG-PARASITE OF THE CURRANT SAW-FLY (NEMA- 

 TUS VENTRICOSUS). 



(Read before the American Association for the Advancement of Science, at its Montreal meeting, 



2gth August, 1882.) 



Dr. Asa Fitch, in his \2th Antiual Report on the Insects of Neiu York 

 for the year 1867 {Trans. N. Y. State Agric. Soc. for 1867, 1868, v. 27), pp. 

 931-932, made the following reference to this insect : 



As none of the foreign accounts which we have seen allude to any 

 parasitic enemy of this currant saw-fl^^ it seemed quite improbable that it 

 would in this country meet with any such enem^^ to lighten from us the 

 task of combatting it and diminishing its devastations. But our valued 

 friend, J. A. Lintner, of Schoharie, greets us with the glad tidings that he 

 has discovered we have such a foe to this formidable scourge. An Gg^^ 

 parasite of this saw-fl)' inhabits our State, an exceedingly minute hymen- 

 opterous insect, which inserts its eggs into those of the saw-fl}'', that its 

 young may subsist upon and consume the contents of those eggs. This 

 diminutive little fly has probably existed hitherto upon the eggs of some 

 one of our American saw-flies similar in size to those of the currant saw- 

 fly ; and it has now discovered that the eggs of this newly-arrived foreigner 

 are equally well adapted to its wants. And so multiplied has this little 

 friend of the gardener become, that in Utica, Mr. Lintner finds that among 

 fifty eggs of a saw-fly upon a currant leaf, there will not be more than 

 four or five that will hatch currant worms, all the rest being occupied by 

 the little maggot, the 3^oung of this parasite. At Schoharie, also, where 

 the saw-flv has arrived more recently than at Utica, he finds this parasite 

 is now beginning to appear. Everj'where this little creature is no doubt 

 following upon the tracks of the saw-fly, and within a very few years 

 after the one arrives in any place the other will be there also, and will 

 speedih^ become so multiplied as to quell and extinguish it. This is a 

 most important discovery, and renders it quite probable that in this coun- 

 try this currant worm can never be but a temporary evil. Whenever cir- 



* For comparison with otlier species of the Cossinm it may be stated that an example of 

 G. Centerensis, ^ , has thirty-eight teeth in the anterior row of the tenth segment, and 

 twenty teeth in the posterior row — the latter, in their entire range, occupying a transverse 

 space equal to that of nine teeth of the anterior row. The teeth are black, shining, irregu- 

 lar in size, and are slightly bent upward over their base ; their length and the distance 

 between their tips exceeds their basal width. 

 28 



