CACTUS-FEEDING INSECTS AND MITES 143 



HABITS AND LIFE HISTORY 



Cochineal insects are conspicuous by the covering of pure white 

 cottony or silky threads of fine waxy filaments secreted by the insects. 

 The covering of D. coccus is light and powdery; but that of all other 

 species is dense and woolly. The North American D. confusus tends to 

 have the heaviest coating. 



The habits and life histories of the various species appear to be very 

 similar, with the possible exception of D. coccus, which has not been 

 studied in this investigation. Observations on the duration of the life- 

 cycle and of the number of generations yearly have been made in North 

 America with D. opuntiae in Texas and Mexico and with D. confusus 

 in Florida; in South America with D. ceylonlcus and Dactylopius sp. near 

 confusus in Argentina; and in Australia with material of the above-men- 

 tioned insects obtained originally from each of the named localities. 

 Furthermore, in Australia the life history of D. opuntiae, and to a less 

 degree of D. confusus, has received considerable attention. The following 

 life history of cochineal is based on my studies of D. opuntiae in 

 Australia. 



The eggs are laid singly beneath the body of the female and hatch 

 in from 1 5 minutes to 6 hours into six-legged active pink or red larvae, 

 termed "crawlers," Newly hatched male and female crawlers appear 

 indistinguishable, but differ in their subsequent development. 



Most female crawlers select a permanent position within 24 to 48 

 hours, commence to feed by inserting the proboscis deep in the plant 

 tissue and remain stationary for their life period. Many settle down 

 around the parent colony, while others crawl to other parts of the joint 

 or the plant. Some, however, may feed at various points over a period of 

 several days before choosing a fixed location. The newly hatched 

 crawlers are capable of living for as long as 10 days without food. 

 They are freely carried by air currents; thus, wind is the main factor in 

 dispersion, and its influence explains the spread of cochineal to isolated 

 plants of prickly pear. 



The female crawlers begin to secrete a woolly protective covering 

 as soon as they settle down. Once the proboscis has been inserted in the 

 plant tissue, the developing insect cannot be removed without breaking 

 that delicate organ and so causing death. The legs shrink and become 

 functionless; the antennae, too, decrease in size. After removal of the 

 white wool, the mature female appears to comprise nothing more than 

 the large segmented abdomen, from which the rudimentary legs and 

 antennae protrude. Maturity, deemed to be reached when reproduction 

 commences, occurs within varying periods; in the summer months the 

 usual time is between 40 and 90 days; in winter, development from the 



