INSECTS ATTAfKlXG \VEEJ)S IN MINNESOTA. 151 



Life History. — The flies have as yet not been observed in tlie 

 held. Full-grown maggots were found within the heads and de- 

 stroying the seeds on August 11 and thereafter. 1die larvae prob- 

 ably enter the soil and pass the winter as pupae. 



Larva. — Length, 4.5 mm. x 2 mm. wide. Color, creamv white 

 except the hind end. which is very dark brown. Two great hooks. 

 Body stout, tapering in front ; surface of body covered with minute, 

 acute granules; fusiform areas indistinct. Anterior spiracles funnel- 

 shaped and ending in 7 or 8 lobes. Anal tubercles apparentlv lack- 

 ing. Two minute circular areas below the stigmal plates. Stigmal 

 plates lighter in color; not noticeably elevated, about their diameter 

 apart ; each composed of three straight slits, radially arranged. The 

 slits are wider at the outer end and notched. 



The Canada Thistle Midge (Dasxncura i^ibsoiii, Felt.j. 



In 1911, (jibson, of Canada, reared a new midge from reddish 

 lar\ae found in the flower heads. These larvae are also present in 

 Minnesota and are apparentl}' the same species. In some parts of 

 Indiana the Canada thistle is reported to have been completely 

 destroyed l)v this little midge. 



PRICKLFA' LFT1TTT{ I Lactuca scariola L.) Insects. 



F/ialoiiia hinitcana, Roljinson. 



The heads of this weed are often infested with small 'I'ineid 

 lar^•ae. Pupae were also present on August 14. one adult having 

 emerged on August 20. The adult moth is a little o\er ^-4 inch 

 long with the fore part of the wing grayish white, while the terminal 

 portion is brownish red with a darker l)r(iwn transverse band. 



Plwbia Sp. 



Although I did not succeed in rearing this fly, the adults were 

 present on the plant. The larvae are common in the heads, feeding 

 on the seeds. 



