231 



Syrphidje 



Chrysotoxum ventricosum Loew. 



This wasp-like fly was found resting on a leaf in the upland for- 

 est (Sta. IV, a) Aug. 26 (No. 163). 



Mesogramma politum Say. Corn Syrphid. 



This fly was taken by T. L. Hankinson in the Bates woods (Sta. 

 IV) June 28, 191 1 (No. 7678). See the prairie list, p. 188. 



Milcsia ornata Fabr. Vespa-like Syrphid. 



This beautiful large syrphid was taken on dogbane in an open 

 space in the upland forest (Sta. IV, a) Aug. 20 (No. 103) ; in the 

 open glade in the lowland forest (Sta. IV, c) Aug. 22 (No. 143); 

 and on Aug. 26 (No. 184) on the flowers of Bupatorium ccclestinum 

 in the clutches of the flower spider Misumena alcatoria Hentz. It 

 was also taken in the Bates woods by T. L. Hankinson June 28, 191 1 

 (No. 7678). Metcalf ('13, p. 73) quotes Verrall as follows con- 

 cerning the subfamily Milesiiiuv: "What little is known about the 

 metamorphism shows that many species live in rotten wood or about 

 the sap flowing from injured tree trunks." 



Hymknoptkra 

 Siricid^; 



Tremex colnmba Linn. Horntail; Pigeon Tremex. 



This species was taken on wing in the upland forest (Sta. IV, a) 

 Aug. 16 (No. 66) ; and on the open slope of a ravine (Sta. IV, b) 

 Aug. 22 (No. 132). 



The larva bores in the trunks of trees, as oak, elm, sycamore, and 

 maple. Consult Packard ('90, pp. 379-381) for a description and 

 figure of the larva. The long-sting, Thalessa lunator, is an external 

 parasite upon this larva (see Riley, '88). I have taken normally 

 colored females at Bloomington, 111., July 25, Sept. 29, and Oct. 8. 

 Two abnormally colored individuals were taken in September, one 

 of them almost, and the other (taken Sept. 29) completely lacking 

 the usual black markings. A female was taken at Milmine, 111., in 

 October. Consult Bradley ('13) for a key to the varieties of this 

 species of Tremex. 



An interesting feature in the ecological relations of this species 

 is the fact that it appears to frequent only weakened, diseased, and 

 dying trees, and these, not as a primary invader, but as a trailer, 

 following insects which have done previous injury to the trees. 

 Felt ('05, p. 61) shows that in New York successive attacks of the 



