51 



Physa and Cambarus were found among the milkweeds on accomit 

 of the wet ground, and the presence of the giant mosquito was prob- 

 ably due to the same condition. The majority of the other animals 

 were attracted to this habitat by the milkweed, particularly by its flow- 

 ers. Among these were the milkweed bugs and beetles, the milkweed 

 butterfly, the honey-bee, and the rusty digger-wasp. The dense growth 

 of the milkweeds does not appear to be so favorable to the garden 

 spider as is the more open and irregular growth of vegetation else- 

 where. The ambush spider frequented the milkweed flowers for prey 

 and also the flower masses of the motrntain mint, on which it was in 

 active competition with the ambush bug and the rapacious soldier-bug, 

 which have similar food habits. The motrntain mint, whose flowers 

 are frequented by the predaceous animals just? mentioned, is also vis- 

 ited by rhipiphorid beetles, the bee-fly (Bxoprosopa fasdata), the bees 

 Melissodes bimaculata and Bpeolus concolor, and the myzinid wasp 

 Myzitie sexcincta. The prairie grasses were frequented by a large 

 variety of Orthoptera, which showed a decided preference for them, 

 their abundance being evident in the list. The wide-ranging predators 

 and parasites, such as Liobunum, UbeUula, Sympetrum, Chrysopa, 

 Brachynetnurus, Promachus, Chlorion, and Myzine, probably forage 

 over extensive areas compared with the relatively sedentary kinds, 

 such as Misumena, Argiope, Phymata, and Sinea. Phymata was cap- 

 tured on a milkweed flower with a honey-bee ; Promachus vertebratus 

 was taken on a grass stem with a stink-bug (Buschistus variolarius) ; 

 and Misumena aleatoria was taken with a large, nearly mature female 

 njnnph of Conocephalus. 



The conditions which permit an animal to breed in a habitat have 

 an important influence upon the character of its population. It is evi- 

 dent that many of the animals taken do not breed here. Some of the 

 relatively sedentary kinds, such as Physa, Cambarus, and Argiope, and 

 probably Misumena, do not cover long distances. Good examples of 

 the wider ranging forms are Sympetrum, UbeUtda, Danais, Proma- 

 chus, Apis, Bombus, and Chlorion. Several of the animals, as the 

 snails, crawfish, and the dragon-flies, require an aquatic habitat. 

 Chrysopa places its eggs among colonies of plant-lice, and Brachyne- 

 tnurus probably spends its larval life in dry or sandy places, feeding 

 upon ants and other small insects, as do other ant-lions. Several of 

 the Orthoptera deposit their eggs in the soil ; and some of the locustids, 

 among grasses and herbaceous stems. Others are found copulating 

 upon the plants on which the young feed, as Tetraopes, Chrysochus, 

 Bygeeus, and Oncopeltus; and stiU others copulate in the flowers 

 norainly, as Phymata. It is probable that on the flowers some of the para- 



