INSECT NOTES FROM MINNESOTA FOB L906. 15 



so treated made an excellent showing. A man can treat 6 to 8 plants 

 2^er minute. This treatment, of course, would not be practicable on a 

 large acreage. 

 The small red mite Trombidium scabrum Say was observed to be 



extremely active in sucking the ogg> of the Phorbia. On May 15 an 

 assistant in the field reported this mite as very numerous averaging 

 about two to a plant, and occasionally four or five were observed 

 about one plant. On this date a large number of egg- examined had 

 evidently been sucked. Frequently there would not be a single good 

 vgg found around a plant, out of a lot of a dozen or more that had 

 originally been laid there. 



We have obtained from the burrow of a maggot a cynipid para- 

 site, Pseudeucoda giUettei Ashm. : we have also bred from a pupa- 

 rium Plectiscvs sp. — identified by the American Entomological 

 Society, of Philadelphia. We have also included among the pre- 

 daceous enemies of Phorbia the carabid beetles Pterostichus coracinus 

 Newm., P. lucublandus Say. Agonoderus pallipes Fab., and Amara 

 impuncticollis Say. since immediately after being brought in from 

 the field these beetles fed ravenously upon the maggot. These species 

 were present in large numbers in almost all of our cabbage fields. 

 as were also Ileterothop* fumigatus Lee. Lathrobium an ale Lee. 

 and Bembidium quadrimaeulatum L., although these three latter 

 beetles were not actually observed to eat the maggot. Plants in sandy 

 soil appeared to suffer more, everything else being equal, than those 

 planted in heavy soil. 



RECENT OBSERVATIONS ON THE USE OF HYDROCYANIC ACID GAS. 



One sometimes has occasion in fumigating mills of small size to 

 drop packages of cyanide into jars containing acid, and at such 

 times the question as to how much time elapses between the drop- 

 ping of the cyanide, inclosed in a double sack, and the giving off of 

 the deadly gas is an important one. Tn doing the work personally 

 I have allowed fifteen seconds as a conservative estimate in this direc- 

 tion and acted accordingly. To place this matter beyond any doubt, 

 however. Ave have this fall made several trials, timing the interval 

 between the dropping of the double bag of cyanide into the jar and 

 the first appearance of the fumes, with surprising results. A double 

 inanila sack was used in each case — that i>. one sack inside another — 

 and various makes of sacks. In each ease the liquid was fairly 

 warm, but no observation was made on its exact temperature. We 

 found in a series of trials that this interval varies from twenty-nine 

 seconds, the lowesl period, to four minute-, the latter being the 

 highest interval, the variation evidently being largely due to varia- 

 tions in the thickness and character o\' the paper of which the sacks 



