60 



FAMILY II. BLATTIDJE. THE COCKROACHES. 



branous, corneous or leathery, usually more or less translucent 

 and, when well developed, overlapping along their sutural mar- 

 gins; in the female of many species rudimentary or sometimes 

 wholly wanting. Four main veins or nervures arise near the 

 basal margin of each tegnien, their position and names being 

 shown in Fig. 30. The wings are always shorter than the teg- 

 mina, but are usually fully developed when the latter are long, 

 though sometimes, even then, rudimentary or absent. When the 



tegmiua are reduced in 

 size, the wings are cor- 

 respondingly smaller. 

 They are membranous 

 in structure, often very 

 delicate, the names and 

 position of their prin- 

 cipal veins being shown 

 in the accompanying 

 digram, Fig. 30. 



The abdomen is large, 

 broad, and composed of 

 ten segments, each with 

 a dorsal and a ventral 

 plate ; however, only 

 seven or eight of these 

 are usually visible. The 

 first one behind the 

 metanotum above is 

 known as the median 

 dorsal segment, the next 

 as the basal or first dor- 

 sal segment. In the males of many species one or both of these 

 have the upper surface more or less specialized or modified. The 

 tenth dorsal plate is known as the supra -anal and its shape and 

 structure are much used in classification. Nine ventral plates 

 are visible in the male and seven in the female, the last one in 

 both sexes being known as the subgcnital plate. This in the male 

 usually bears near its apex two small unjointed appendages called 

 styles. The tenth dorsal segment also bears a pair of jointed 

 appendages known as ccrci, which vary much according to species, 

 in length, number of joints, etc. The rings or segments of the 

 abdomen overlap each other and are capable of great extension 

 and depression, so that these insects seem to be pre-eminently fitted 



Fig. 30. Diagram of the left tegmen and wing of 

 a Blattid. i, Marginal field; 2, scapular field; 3, 

 discoidal field; 4, anal field; 5, anterior field; 6, 

 intercalated triangle; 7, posterior field. Ms. 

 Mediastine vein; D, discoidal vein; C, costal veins; 

 M, median vein; Mr., branches of median vein; U, 

 ulnar vein; A, anal sulcus; Ax, axillary vein; R, 

 radiate veins. (After Hebard.) 



