CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS I39 



A A. Front wings with three oblique veins, the media simple (unbranched), 

 radial sector merged with margin of stigma; antennae never more than 5- 

 segmented. 

 B. Antennae s-segmented; wings at rest folded upright; galls on conifers. 

 — Chermes. 

 BB. Antennae 3- or 4-segmented; wings at rest flat on back; galls on grape, 

 hickory, etc., never on conifers. — Phylloxera. 



Sc*RtM*Cu* 1st A 5c 



Sc^R*M*Cu*lstA Sc 



Fig. 91. — Venation of Macro- 

 siphum. (After Patch.) 



Fig. 92. — Venation of Toxoptera. 

 (After Patch.) 



Plant-lice or Aphids are gregarious sucking insects, often abundant 

 on many varieties of plants, and doing much injury. Three forms 

 occur: i. sedentary wingless viviparous agamic females, 2. migra- 

 tory winged viviparous agamic females, 3. sexual males and females 

 — the females oviparous and wingless and the males winged or wingless. 



Sc*R-'M*CuflstA Sc 



5c*R^M*Cu*lstA - 



4 —5c 



Fig. 93. — Venation of Telra- 

 netira. (After Patch.) 



Fig. 94. — Venation of Chermes. 

 (After Patch.) 



Reproduction among the aphids may be represented diagrammatic- 

 ally as follows: 



O— P— P— P— P— P— P— P— P(^ ^0 



9 



= P = P_P— p_P— p/ \o 



9 

 where represents the overwintering egg, P the viviparous agamic 



