THE AMERICAN ENTOMOLOGIST. 



131 



Parasites of the Plum Curculio. — Some of 

 the members of oiir Itliaca Farmers' Cluli say that 

 you know of an insect which will kill out the 

 Plum Curculio completely in three years, if intro- 

 duced and cultivated. They wish to know if 

 this is so, and to cultivate such enemy to the Cur- 

 culios which have heen uncommonly injurious 

 here the past season. For them 1 make the 

 above inquiry, but am inclined to think some- 

 bod}' has misunderstood vou. — W. S. Barnard, 

 Ithaca, N. Y. 



The statement alluded to by our correspondent 

 is undoubtedly based upon what we wrote nearly 

 ten years ago on certain parasites of the Plum 

 Curculio, having {3d Missouri Report, pp. 24-29) 

 there shown that there were two such in existence. 

 We quote portions of our account of the most 

 common and wide-spread of these parasites and 

 herewith introduce figures which will cause them 

 to be recognized ; 



Just 10 [now 20] years ago, in his "Address on 

 the Curculio," delivered at the annual meeting of 

 the N. Y. State Agricultural Society, Dr. Fitch 

 gave an account, accompanied with a figure, of a 

 small Ichneumon-fly which he named Sit;a//>/iiis 

 curculioiiis, and which he believed was parasitic 

 on the Curculio. Before that time no parasite 

 had ever been known to attack this pestilent 

 little weevil, and even up to the present time it 

 is currently believed that no such parasite exists ; 

 for unfortunately the evidence given by Dr. Fitch 



LFig. 49.; 



.SiGAl.HHUS CURCULlONis ;- 



(after Riley). 



larva ; b^ cocoon ; r. pupa 



was not sufficient to satisfy some of our most 

 eminent entomologists. These parasites were in 

 fact received by him from Mr. D. W. Beadle of 

 St. Catherines, C. W., who had bred them from 

 Black-knot, from which he bred at the same time 

 a certain number of Curculios ; but as other 

 worms besides those of the Curculio are likewise 

 found in Black-knot, we had no absolute proof 

 that this fly was parasitic on the insect in question. 

 Consequently we find that Mr. Walsh, in his Re- 

 port as Acting State Entomologist of Illinois, 

 rather ridicules the idea of its being a Curculio- 

 pyphen parasite and endeavors to prove that it is 

 parasitic instead on the larva of his Plum Moth 

 \S(masia pntiiivora). But I have this year not 

 only proved that poor Walsh was himself wrong 

 in this particular inference, but that he was 

 equally wrong in supposing his little Plum Moth, 

 so called, to be confined to plums : for I have 

 bred it from Galls {Qnctcus fnniilflsa Bassett) ; 

 from haws, from crab apples, and abundantly 

 from tame apples. 



To be brief. Dr. Fitch's Sigalfhus is a true 

 parasite on the Plum Curculio and I have bred 

 hundreds of the flies from Curculio larvae. The 

 first bred specimens gave me much pleasure, for 

 as soon as I saw they belonged to the same genus 

 as Dr. Fitch's fly, I felt assured that another dis- 

 puted question was settled. But to make assur- 



ance doubly sure, I repeatedly half filled large 

 jars with pure earth, finely sifted so that no liv- 

 ing animal remained in it. Into these jars I 

 placed Curculio larvae from day to day as they 

 issued from peaches that were thrown into 

 another vessel, and in due time the parasitic flies 

 began to issue from the ground along with the 

 perfect Curculios. Nay more than this, I soon 

 learned to distinguish such Curculio larva: as 

 were parasitised, and after they had worried 

 themselves under the ground — seldom more than 

 half an inch — 1 would uncover them, and on 

 several occasions had the satisfaction of watching 

 the gnawing worm within reduce its victim until 

 finallv nothing was left of him. As soon as the 

 Curculio larva is destroyed by the parasite, the 

 latter (Fig, 49, a) encloses itself in a tough little 

 yellowish cocoon of silk (Fig. 49, h), then gradu- 

 ally assumes the pupa state (Fig. 49, c) and at 

 the end of about the same length of tiine that the 

 Curculio requires to undergo ils transformations 

 and issue as a beetle, this, its deadly foe, gnaws 

 a hole through its cocoon and issues to the light 

 of day as a black four-winged fly (Fig. 50,17, male; 

 b, fc'fiiale). In the vicinity of St. Louis, this fly 

 was so common the past season, that after very 

 careful estimates, I am satisfied three-fourths of 

 all the more early developed Curculio larvae were 

 destroyed by it. 



As Mr. Walsh bred this same parasite from the 

 larvae of his little Plum Moth, it doubtless at- 



[Fig. .W.] 



SlOALl'Hes CURCULlONis: — rt. male, tlni-sal view; <^, female, 

 side view (after Riley). 



tacks other soft-bodied larvae and does not con- 

 fine itself to the Plum Curculio. This is the 

 more likely as it would scarcely pass the winter in 

 the fly state. The female, with that wonderful in- 

 stinct which is exhibited in such a surpassing de- 

 gree in the insect world, knows as well as we great 

 Lords of Creation what the little crescent mark 

 upon a peach or plum indicates ; and can doubt- 

 less tell with more surety, though she never re- 

 ceived a lesson from her parents, whether or not 

 a Curculio larva is drilling its way through the 

 fruit. When she has once ascertained the pres- 

 ence of such a larva by aid of her antennx — which 

 she deftly applies to diflerent parts of the fruit, 

 and which doubtless possess some occult and 

 delicate sense of perception, whicli, with our 

 comparatively dull senses, we are unable to com- 

 prehend — then she pierces the fruit, and with un- 

 erring precision, deposits a single egg in her 

 victim, by means of her ovipositor. 



Now there is a variet)' (ni/iis) of this parasite, 

 with the ovipositor nearly one-fifth of an inch 

 long, but in the normal form the ovipositor is 

 only twelve-hundrcdths of an inch long, and the 

 Curculio larva must therefore be reached soon 

 after it hatches, or while yet very young. Conse- 



