442 



the nymph to the adult and is carried about by the latter until it is 

 nearly mature, when it escapes again into the water for the final stage. 

 A.nother mite has been reported to feed upon the eggs of Anisoptera, 

 but this statement has not been verified for the Zygoptera. Needham 

 ('03) says that a large number of hymenopterous parasites prey on 

 the eggs of Lestes, left exposed above the water-line, and he reared 

 the following species: Brackista pallida Ashm., Ccntrohia odonatae 

 Ashm., and Polyncma nccdhami Ashm. Brandt ('69) also reports 

 rearing Polyncma ovidorum from the eggs of Agrion (Calopteryx) 

 and says that as many as fifty per cent, of the eggs were sometimes 

 destroyed by this parasite. 



A fungus belonging to the Saprolegniales frequently attacks the 

 nymphs, especially if enfeebled from any cause. Sometimes it be- 

 comes very difficult to rear specimens, and if the rearing-jars become 

 infected nothing short of thorough sterilization will be of any avail. 

 This fungus is related to the one attacking fish and causing great 

 damage in hatcheries. It is also known to attack the larvae of Coryd- 

 alis. 



Emergence of Adult. — When the nymph has molted a stated 

 number of times, somewhere between ten and fourteen, and has be- 

 come full-grown, it crawls out of the water, dries its cuticle, which 

 soon splits along the mid-dorsum of the thorax and head, and the 

 adult emerges. The nymphs of Zygoptera usually seek the sunlight 

 to transform and emerge early in the morning, the greater number 

 being clear of the skin before eight o'clock. A much smaller nimi- 

 ber have been seen to emerge after six o'clock in the evening or late 

 in the afternoon, but very few, if any, emerge during the heat of the 

 day. The emergence follows a more or less definite schedule. When 

 first out of the nymphal skin, the parts of the body are no larger than 

 the parts of the foregoing nymph, and the insect is yellowish green 

 in color. Great changes soon begin, including an elongation of the 

 abdomen and wings as well as enlargement of other parts, and within 

 an hour the insect is ready to take flight. At this time it may show 

 mature coloration or the color may still be incompletely developed, 

 and in this condition the adult is known as teneral. The teneral state 

 may last for several days or longer, depending somewhat upon the 

 amount of sunlight to which the insect is subjected, or there may be 

 no further change after the power of flight is attained. Bnallagma 

 exsulans, B. gcminatnm, and the male of Ischnnra vcrticnlis are ex- 

 amples of species which apparently have no teneral state. Enallagma 

 carunculatum, and Ischnnra verticalis, female, are examples of spe- 

 cies which apparently have a long teneral period. The change from 



