NATURAL CONTROL. 47 



list of the birds occurring in the boot holds, which liavo been 

 proven to be insectivoro.us.^ Those marked (*) were especially 

 abundant: 



Killdeer {O.ri/echus rociferus). 



* Valley ([uail {Lophorty.r californicus valUcola). 

 Western nighthawk (Chordeiles virginianus henryi). 

 Ash-throated flycatcher {Myiarchus cinerascens dnerascen^). 



* Western meadowlark (Sturnella neglecta).- 



* Brewer's blackbird ( Euphagus cyanocephalus) . 



* Native sparrow. 



* California shrike (Lanius ludovicianus gambeli). 



Next to the birds as insect destroyers can be ranked the predaceous 

 beetles belonging to the family Carabidse, or ground beetles. Only 

 two were notedj Calosoma cancellatum Esch. and C. semilxveLiec., but 

 these proved to be important factors in the control of the beetles. 

 Both of these occurred commonly throughout southern California. 

 Sometimes as many as 15 to 20 would be noted in a single collecting 

 trip. Calosoma cancellMum occurred in the greater numbers. 



These })redatory enemies are able to dispose of a large number of 

 adults daily, as many outdoor observations proved. In one instance 

 the examination of a large beet gave 31 live elaterids, 1 C. cancel- 

 latum, antl the remains of 117 elaterids. This beet had been exam- 

 ined just two days previously, so this represented not more than two 

 (hiys' work. The rapidity of the wa)rk may bo judged from the fact 

 that the remains of a dozen of the elaterids were still moving their 

 legs feebly when discovered. 



The carabids in feeding never touch the head or thorax, but bite 

 off all or a part of the abdomen. As the abdomen, except when filled 

 with eggs, contains little food it is readily understood how these 

 ground beetles are able to destroy so many elaterids a day. The 

 carabids did most of their feeding while the tilaterids were in their 

 secondary hibernation or early feeding period. They were especially 

 valuable at this time, as they could dig under the beets and destroy 

 the beetles collected there. 



These predaceous enemies — carabid beetles and birds — make a very 

 good combination, as the beetles are an effective check early in the 

 season, and later, when the elaterids are moving through the fields, 

 the birds are at their best. 



Sudden and very severe storms probably act as further checks, but 

 in a mild year, such as 1912, very few beetles were found to have been 

 killed in the field. The adults are also attacked by a fungous dis- 

 ease. This disease works well under laboratory conditions, but less 



' See Senate Document No. 30.5, 62d Congress, 2d Se.ssion, p. 14, 1912. 



- Mr. Brj'ant, in the Pomona Jonmal of Entomology, vol. 4, No. 3, speaking of the western meadow- 

 lark, says, "Ground beetles are taken each month of the year." He then names Limonius californicus 

 among those taken. 



