INSECTS ATTACKING WEEDS IN MINNESOTA. 141 



Phorhia Sp. 



Occurring- very abundantly in tlie pods on August 30 were 

 dipterous larvae. These are very voracious, for they consume most 

 of the seeds. The pods turn brownish when infested by the mag- 

 gots, which make conspicuous exit holes when full grown. I did 

 not succeed in rearing the adults, but those of Plwrbia sp. were 

 present al)Out the pods on July 12th and may be the parent form. 



There is no doubt but that these insects infesting the pods 

 destroy most of the seeds and help to keep this w^eed in check. 



EVENING PRIMROSE {Oenothera biennis L. ) Insects. 

 The Evening Primrose Beetle (Tyloderma fovcuiata. Say). 



This species was reported in 1897 as very injurious on straw- 

 berries in i'ritish Columbia, the grubs attacking the crown simi- 

 larly to T. fnigaria and breeding also in willow herbs. Webster 

 records its oviposition habits similar to that of T. fragaria. 



Oviposition. — After finding a suitable place, the female bores 

 a small hole in the stem with her snout. She then turns around 

 and places an egg within the cavity ; after the egg is laid, the 

 female proceeds to cover it up, resting directly over the egg, and 

 remaining in this position without moving the feet until the process 

 is completed. About j/^ inch away from the egg a shred of tissue 

 is taken up with the beak and carefully placed over the egg. This 

 is repeated many times until the egg is completely covered, when 

 the female turns around and l:)egins tlie same operation at the oppo- 

 site end. Oviposition lasts abotit 25 to 30 minutes, and when 

 completed, a conspicuous scar is left on the stem. Such a scar will 

 measure about 6 mm. long and 4 mm. wide, the central portion of 

 wdiich is somewhat elevated and brownish, while above and below, 

 shallow cavities exist. These scars may be made anywhere on the 

 stem from the bottom to the top, and as many as 30 or 40 may 

 be present. 



Life History. — The beetles were first observed on June 7, ovi- 

 positing and making their scars on the stem. Egg, larvae, and 

 adults may be found throughout the greater part of the summer. 

 On August 29, pupae w^ere already present within the stem, while a 

 few days later, adults emerged. There is one generation a year 

 and the winter is passed in the adult stage. 



Pupa. — Whitish, except eyes in mature pupa. Four large 

 bristles on snout, and four on the head, all of wdiich are arranged 

 in two longitudinal rows. Anterior margin of thorax with four 



