48 BULLETIN 351, U. S. DEPARTMENT OF AGRICULTURE. 



importance. This period of excretion extends to the time of hiber- 

 nation, but practically all the honey dew is deposited during the first 

 25 days. 



The anal apparatus is specially adapted to the excretion of honey- 

 dew. The anal plates, which are situated near the posterior end of 

 the derm, are so hinged at their anterior ends that they can be both 

 elevated and separated. When in this position they expose the anal 

 chamber which lies just below them. This chamber is bounded, 

 laterally by the body lobes and connects ventrally with the brood 

 chamber, while a cloacal cavity extends forward, within which there 

 is a retractile spindle-shaped rectum, at the distal extremity of which 

 the anal aperture is located. It is surrounded by a fringe of eight 

 filaments called the anal ring. During repose the rectum occupies 

 the anterior part of the cloacal cavity, and the anal fringe, which is 

 folded into a cylindrical mass, occupies the posterior part. When 

 the scale is not excreting the anal cavity is empty and closed at 

 the top by the lidlike anal plates. Preparatory to excretion the anal 

 plates are elevated and separated; the rectum with its fringe is 

 drawn backward from the cloacal cavity into the anal chamber, from 

 which it is thrust through the opening between the elevated anal 

 plates. Contraction of the muscular walls of the rectum causes the 

 contents to ooze into the basket formed by the filaments of the anal 

 ring, where it forms a bubble which is held in place upon the end of 

 the rectum by the supporting filaments, much as a jewel is held in 

 its setting. When the bubble is fully formed it bursts, hurling the 

 liquid composing it in the form of minute drops to a distance of from 

 3 to 8 inches. Cohesion between the honeydew and the filaments of 

 the fringe is very slight. As a result no honeydew remains upon the 

 fringe after the bursting of the bubble. The rectum is always with- 

 drawn and the anal cavity closed after each expulsion. The deposit 

 of honeydew from the twig-attached females becomes noticeable in 

 orchards during the first week in August and rapidly increases in 

 amount during the remainder of the month. At Midvale, Pa., in 

 1913, the deposit was first noticed August 4. It was made by the 

 few advanced females then upon the twigs. The amount excreted 

 reached its maximum on August 23, after which the amount upon 

 the trees remained nearly constant until the first week of September. 

 The sooty fungus which develops upon this honeydew increases in 

 abundance with the increased deposit, and by the end of August its 

 black spores have transformed the transparent honeydew into a 

 sooty paste. By the end of the first week in September the leaves, 

 branches, and fruit are covered by a black film of dried honeydew 

 and spores. In some cases the infestation is so severe that the soil 

 under the tree is coated almost as thickly as the limbs. The deposit 



