NO. 1310. NORTH AMERICAN THYSANOPTERA— HINDS. 83 



and Aphidpe. In the structure of the mouthparts, the Physapoda are not as far 

 reniov'ed from the Orthoptera as are the Rhynchota; the Physapod prol)OScis is of a 

 tyjie between the biting mouthparts of Orthoptera and the sucking mouth of the 

 Rhynchota, l)y which it is not meant that the Homoptera have developed from our 

 Pliysapoda. The biting mouth organs of the Orthoptera are here concealed by the 

 transformation of the mandibles into piercing bristles and the growing together of 

 the labrum with the maxilke and labium, while the piercing bristles form a short 

 tube to the sucking iiroboscis. In this respect the Physapoda should be considered 

 as Rhynchota together with the Homoptera and Heteroptera. 



Thrips have the free prothorax in common with the Orthoptera s. 1. and the Ryn- 

 chota. The development of the meso and metathorax shows that at lea.«t the meta- 

 sternum and mesosternum are nearly equal to those in the Orthoptera, while the 

 absence of the metaphragma, which is always present in the Orthoptera, and the dis- 

 appearance of the long metathoracic muscles which are not reduced there, bring 

 Thrips into close connection with the Homoptera. The first ventral ring is main- 

 tained through the absence of the first ventral plate and the entrance of the dorsal 

 plate into the thoracic covering in the Phj-sapoda just as in many Orthoi^tera s. 1., 

 but a quite similar condition is also shown in the first abdominal segment of the 

 Homopterous Ps3-llid;p, a sign that Orthopteroid characters may be retained even in 

 genuine Rhynchota. 



A reduction of the system of venation of the wing takes place in the Phytophthira 

 as in the Physapoda, but not in the same degree in the Orthoptera s. 1. Th- i'hysapod 

 wing is a Phytophthiran wing in which the large spread is greatly reduced, as in the 

 Pterophoridje, by the development of long fringes. 



In regard to the concentrated nervous system, Thrips come veiy close to Rhyn- 

 chota and are far removed from the Orthoptera, but in this connection it is worth 

 noting that the aberrant Mallophaga, pn^vided with biting mouth parts, also possess a 

 concentrated nervous system. Aside from these doubtful cases, all other Orthoptera 

 have a developed chain of ventral ganglia. The tracheal system of Thrips has the 

 small number of three or four pairs of stigmata. We find the stigmata reduced 

 usually in the breathing organs of holometabolous insects. Among the Rhynchota we 

 find it as in the Coccidae; all other Rhynchota and the Orthoptera are holopneustic. 

 The alimentary canal of Physapoda is characterized by the possession of four mal- 

 pighian vessels which occur in like manner in all Rhynchota with the exception of the 

 Aphidaj which have none, and the Coccidae which have two urinary organs. The 

 Orthoptera have a large number of urinary tubes, with the exception of the Termi- 

 tid:p and Psocidte with six and the Mallophaga with four. The long, slender oeso- 

 phagus of Terebrantia which reaches even into the abdomen is found also in the 

 Psyllida^, the large loop of the midgut of Terebrantia is characteristic of many Homop- 

 tera, but in these the enlargement of the loop of the gut running back, takes place 

 at the beginning of the midgut. 



The male sexual apparatus, with its simple, often pear-shaped testes, resembles the 

 Mallophaga about as much as the Phytophthira; the female organs, from the rosette 

 arrangement of the ovarian tubes, resembles the tubes in the Rhynchota; the want 

 of connective strands of the eggs with the germ area places the ovaries esi)ecially 

 beside those of theCicadellin;e. The genital armature of the Terebrantia is found in 

 the Orthoptera and Phytophthira. 



In anatomical respects, therefore, the Physapoda come nearer the Homoptera than 

 the Orthoptera s. 1. There is also a series of biological facts which strengthen still 

 further the connection of these insects with the Homoptera. First, I would recall 

 that the Physapoda with their nymph and pronymph stages, in which they take no 

 nourishment, exhibit a very similar transformation to that which is known to take 

 place in Coccid males. The parthenogenesis of Thrips is not Orthopteroid, but a 

 method of reproduction which is peculiar chiefiy to the Phytophthira. The frequent 



