THE WESTERN CABBAGE FLEA-BEETLE. 



LIFE HISTORY AND HABITS. 



OPPOSITION. 



Opportunity was afforded for observing the female of this flea- 

 beetle in the act of laying her eggs, beginning June 18, 1915, at Rocky 

 Ford, Colo. In a period of 12 minutes 17 eggs were deposited. When 

 fully extruded, the ovipositor is from one-third to one-half the length 

 of the abdomen. The total time taken in laying an egg varied from 

 2 to 5 seconds, 3 seconds being the average. During the laying there is 

 a contracting movement of the abdomen, the ovipositor is extruded — 

 not always to its full length — and an egg is forced through the 

 opening. If, when the egg is forced out, it does not strike a surface 

 and adhere to it the female twists the ovipositor about until the egg 

 comes into contact with a surface to which it adheres. After an egg 

 was laid the female generally ran about for a few seconds, then 

 stopped and remained quiet for a few more seconds before laying 

 another egg. Three different times the succeeding egg was laid at 

 the same place within 3 or 4 seconds of the preceding one. As far 

 as could be determined the eggs were not deposited in any particular 

 order or arrangement, but were distributed quite promiscuously 

 over the surface of the glass in the rearing cage. After having laid 

 the last egg, the female ran down on the stem of a turnip leaf, which 

 was in the cage, and commenced to eat. No further egg laying was 

 observed, but as four other eggs were found it is presumed that they 

 were laid before these observations began, which would give a total 

 of about 21 eggs laid at this time. 



Subsequently eggs were found in various other locations, one mass 

 of 20 being laid on the soil, another of similar number on the lower 

 surface of a turnip leaf, while others were scattered in small masses 

 about the crowns of the plants. 



The number of eggs that might be deposited by a single beetle was 

 very difficult to ascertain and although attempts were made only 

 two records of egg laying were obtained. 



September 6, 1915, three beetles, two females and a male, developed 

 ,in the cages at Rocky Ford, Colo. They lived through the winter 

 under bits of earth in a rearing jar, and March 29, 1916, the male 

 mated with one of the females. This pair was isolated in another 

 cage and the record of the eggs deposited is given in Table I. 



Table I. — Egg-laying record of a single female of Phyllotreta pusilla. 



Date. 



Number 



of eggs 



deposited. 



Date. 



Number 



of eggs 



deposited. 



1918. 



21 

 27 

 23 

 23 

 16 

 15 



1916. 

 May 21 



25 



29 



June 6 



19 

 32 

 27 

 21 

 20 



12 



21 



29 



May 6. 



13 



Total 



9 



244 





1832°— 20- 



