58 MAINE AGRICULTURAL EXPLRIMENT STATION. I912. 



Florists look upon these little gnats with a suspicion which is 

 more than justified, as the fact that the larvae feed upon the 

 tender roots of potted plants is well established. Sciara tritici 

 is identified with an injury to the roots and stems of wheat, 

 and it is probable that the damage caused by it or by some other 

 member of this genus is far more widespread than is generally 

 known owing to the insidiousness of its attack. 



In Bulletin 27, n. s. (U. S. Dept. Agr. Div. of Entomology) 

 Mr. Chittenden cites several instances of damage occasioned 

 by S. inconstans to peas growing in flower pots, and to lettuce, 

 cucumbers, and carnations. The injury caued by S. inali is 

 according to Fitch's OAvn account, secondary in its nature, the 

 larvae feeding on apples already aft'ected by the Codling moth. 

 It may be moreover only an accidental occurrence, as there is 

 no record in entomological literature, as far as I know, of a 

 similar attack. Benj: Walsh's Grape J\Iidge (First Ann. Rept. 

 111. 21, 1867) belongs in the same category, it being a guest of 

 more injurious species. 



Walsh and others have long ago suggested the possibility 

 that the larvae of some species of Sciara are associated in some 

 way with a sort of potato scab. The fact that the larvre ot 

 these gnats are so abundant in barnyard manure and that scab 

 is most prevalent on potatoes from fields which have been well 

 fertilized has suggested the possibility of this relationship. ]\Iost 

 significant in this connection is the account given by Dr. A. D. 

 Hopkins of Pnyxia (Epidapiis) scabiei. Concerning this species 

 he says : "I have observed the larvcT of a Sciara and an 

 Epidapiis feeding on the living, healthy tissue of potato tubers, 

 and have obtained conclusive evidence that tbe}^ are capable of 

 causing, and actually do cause, conditions wdiich ni one stage 

 would be recognized as potato-scab and in a more advanced 

 stage would be recognized as a form of potato-rot." 



From the context of Mr. Hopkin's article it is not necessarily 

 inferred that he associates that form of potato scab caused by 

 Oospora scabiei with the injury (or infection) produced by the 

 insect. 



My own observations of the larvse of Sciara confirm the 

 statements made by some of the earlier writers. I have found 

 larvae in potatoes feeding on the sound tissue, on the roots of 

 various grasses and in tulip bulbs. In some preliminary experi- 

 ments I failed to induce larv^ to attack a tuber wuh unbroken 



