THE RED SPIDER ON THE AVOCADO. 
Table 4. — Length of the second nymphal stadium. 
No. 
Date 
emerged. 
Date 
molted. 
Dura- 
tion. 
Mean 
temper- 
ature. 
No. 
Date 
emerged. 
Date 
molted. 
Dura- 
tion. 
Mean 
temper- 
ature. 
1 
2 
3 
4 
5 
6 
Oct. 22 
Nov. 3 
Nov. 23 
Dec. 18 
Jan. 1 
Jan. 18 
Oct. 25 
Nov. 6 
Nov. 25 
Dec. 21 
Jan. 4 
Jan. 24 
Days. 
3 
3 
2 
3 
3 
3 
°F. 
76 
77 
75 
70 
68 
63 
8 
9 
10 
11 
12 
Feb. 6 
Feb. 26 
Mar. 25 
Apr. 9 
June 8 
July 16 
Feb. 10 
Feb. 29 
Mar. 28 
Apr. 12 
June 10 
July 18 
Days. 
4 
3 
3 
3 
2 
2 
°F. 
65 
70 
72 
75 
76 
79 
BIOLOGICAL DATA. 
Webbing. — Unlike the majority of red spiders this species does not 
spin an extensive web and carries on its depredations on the foliage 
practically unprotected. The only indications of any webbing made 
by this species are the mere fibrils attached to the apex of the eggs 
when deposited (fig. 3, a). 
Average length of life period. — The length of the life period of the 
adult mites varies greatly with the season and temperature and possi- 
bly other conditions. Experiments on the life history of this species 
showed that adults emerging November 25 came to their natural 
death during the period January 1 to 15, while those emerging June 
10 succumbed between July 1 and 15. This shows that during the 
dry winter months approximately two months are required from the 
time of emergence to the completion of the life period, while during 
the humid summer months approximately a month is required. 
Molting process. — Before molting the mite securely attaches itself 
to the leaf. In emerging from the quiescent stage the old skin splits 
transversely along the cephalothoraeic-abdominal suture. Following 
the splitting of the skin the anterior end of the mite is slowly drawn 
from the old skin. With the use of its fore legs the mite forces its 
way out from the shell. 
Parthenogenesis. — Some immature individuals were isolated on a 
number of plants. From these individuals virgin females were ob- 
tained. These females produced eggs and in each instance the re- 
sultant individuals were males. 
Migration. — There does not seem to be an alternate host of this spe- 
cies. Individual red spiders may be found on the avocado at any time 
during the year in varying numbers, and never leave the tree for want 
of a new or alternate host plant on which to feed. In a grove the red 
spiders are spread from tree to tree by the wind, birds, etc. 
Generations of the species. — The generations of the avocado red 
spider fluctuate as to number and overlap considerably. In years of 
little rain during the fall the red spiders come in evidence more 
quickly than when rains occur earlier. Intermittent rains frequently 
