■AND OTHER INJURIOUS INSECTS OF I907 AND I908. 187 



The lateral tubercles are found on the first eight segments in most 

 of the higher genera. They are of different shapes and may be of 

 value for specific characters. In the simplest form there is only a 

 single small rounded tubercle, but sometimes, as in Chaitophorus 

 spinosa, there are two, three, or four of these tubercles close together. 

 In some species certain of the tubercles are of considerable length. 

 In Aphis syuiphoricarpi the tubercles are not present, but there is a 

 large circular transparent area which probably represents them. 



The glands are found in the gall-formers principally. They may 

 be on the dorsal side of every segment of the body except the ninth 

 abdominal, or only on a few segments. There may be as many as six 

 longitudinal rows or only two, so that they are of value in classifica- 

 tion probably for specific characters. 



The hairs are of several kinds. There are the slender curved body 

 hairs, which may be either fine or coarse ; the thick, spine-like hairs 

 of Chaitophorus spinosa; and glandular hairs with knobbed tips. These 

 last show several variations. In the larva of Siphocoryne xanthii they 

 are short with large swollen ends and raised bases. In Chaitophorus 

 and Callipterus they are long and only slightly swollen at the tip. In 

 Macrosiphmn they are of medium length and have spatulate tips. The 

 dimorphous forms of Chaitophoriis are armed with peculiar modified 

 hairs (flabell?e) which have been described by Bucton and other 

 authors. These hairs are flattened out into fan-like organs which show 

 several longitudinal rib-like markings. 



The cuticle of the abdomen is usually ornamented with rows of 

 minute points similar to the imbrications of the antennae. Sometimes 

 there is also a, network of hexagonal markings, which are probably a 

 specialized condition of the ordinary ornamentation. 



The Cornicles: The cornicles are situated on the fifth ab- 

 dominal segment. Lachnus exhibits the most primitive cornicle, which 

 has been called the tuberculate type. The body wall in this case is 

 raised into a large round hairy tubercle. The opening is raised slightly 

 above this tubercle so that this cornicle is composed of two parts, the 

 broad, hairy proximal part, arid the narrow, hairless distal part. This 

 has not been distinguished before from the short broad cornicle found 

 in Callipterus and Chaitophorus, which may be called the truncate 

 cornicle. This type does not have the hairy basal part. A third type 

 of cornicle is the cylindrical, which is long, slender and uniform in 

 diameter. The truncate and cylindrical cornicles were probably devel- 

 oped directly from the tuberculate type. The incrassate or fourth 

 type of cornicle is only a modification of the cylindrical form. This 



