THE SPINACH FLEA.-BEETLE. 83 



and others laid on the 23d produced larvae on the 30th, giving seven 

 days as the minimum period. It will probably be found that this 

 period in cooler weather will be extended to nine or ten days, accord- 

 ing to atmospheric conditions at the time that deposition and hatching 

 takes place, and variation being natural in a species where oviposition 

 practically extends throughout a season. Oviposition was actually 

 observed between April 17 and the first day of June, and again in 

 July, beginning on the 22d, and continuing through that month and 

 August. 



The escape of the larva from the egg takes place through a simple 

 longitudinal slit on one side, extending from near the base to the 

 center of the egg. (See fig. 19,6.) 



Larvae kept under nearly natural conditions were obliged after 

 hatching to travel 2 inches to the stem of the food plant provided 

 them, a potted Chenopodium, and at least 5 inches farther before 

 reaching a leaf. As the larvae grow, the social tendency becomes less 

 noticeable, and individuals may be seen here and there on a plant 

 occupying a single leaf. A larva, as a rule, will remain on a leaf until 

 it is full of holes, the sizes of the holes increasing with the growth of 

 the insect. Generally also the larvae feed on the lower surface of a 

 leaf, but not exclusively. 



The gregarious habit of the larva is pronounced from the first. 

 Larvae which hatched in close quarters in confinement gathered in a 

 group on one side of their rearing dish, and another lot which hatched 

 out on cultivated Chenopodium traveled from one leaf to another, 

 seldom being found singly during the early period of their growth. 



One lot of ten larvae, which was observed to hatch June 8, was kept 

 rather closely confined and fed at first upon chickweed and afterwards 

 upon spinach leaves. June 18, or in ten days from the hatching of 

 the eggs, about half had attained full growth, and on the 20th all but 

 one had entered the earth for pupation. On the 27th two individuals, 

 which we may call Nos. 1 and 2, were found to have pupated. No. 3 

 pupated June 28 about 4 p. m., and No. 4 transformed about 11 a. m. of 

 June 29. Nos. 1 and 2 were found to have issued as adult July 5, 

 No. 3 died, and No. 4 transformed to a beetle July 5, being still uncol- 

 ored when first observed at 9 a. m. This last gives us six days as the 

 duration of the pupal state, probably the minimum period, as the 

 weather was extremely hot, the thermometer out of doors having 

 passed the 100° mark during three days of this time. The first two 

 beetles issued during a two days' closing of the office, but it is certain 

 that the date of issuance was July 3. 



It is more than probable, judging from the present experience with 

 this species, that the duration of the larval stage varies considerably 

 according to environment. An attempt to rear larvae, which hatched 

 June 4, on the potted Chenopodium previously mentioned, was not 

 entirely successful, owing to the plant being disturbed. All of the 



