ART. 17. LARVAE OF HOLARCTIC TIGER-BEETLES— HAMILTON. 13 



the species which have three setae on this U-shape ridge there may 

 occasionally be one or two extra setae present. These are usually 

 small and in a few cases the third seta is not prominent. In the 

 genus Tetracha there are three prominent setae on the transverse 

 ridge at the caudal part of the f rons wliile in the genus Omus there is 

 a single large, median seta with one or two smaller setae on each side. 

 The setae on the proximal and second segments of the antennae vai^ 

 within the limits given in the descriptions but usually not more than 

 one on either side of the average. Setae on the hooks of the fifth 

 abdominal segment are constant in number for those species which 

 have two, but vary in those species which have three or more. On 

 each side of the meson at the caudal margin of the ninth abdominal 

 sternum is a transverse row of three, four, or five setae. These 

 setae are constant and furnish good taxonomic characters. 



The dorsal aspect of the head and pronotum is very highly colored 

 in many of the species and, within certain limits, furnishes excellent 

 means for separating them. The color is of two kinds, pigmental 

 and physical. The pigmental colors are dull, usually some shade 

 of brown, and appear the same when examined from any angle. 

 The physical colors are much brighter and are produced by small 

 pit-like depressions. These colors vary with the angle from which 

 the specimen is examined. The surface, when examined with a strong 

 light, may show any of the following colors: Purple, purplish- 

 bronze, coppery, coppery-bronze, bronze, blue, and green. When 

 viewed from an obtuse or acute angle the blue or green color is 

 usually more pronounced and this is spoken of as the color which is 

 reflected. 



GENERAL DISCUSSION OF LIFE HISTORY AND HABITS OF LARVAE 



The larvae of this family differ from the larvae of most other 

 predaceous insects in that they live in a definite fixed burrow and 

 lie in wait for their prey. This habit has made them dependent upon 

 chance for their food supply and undoubtedly it is very irregular 

 and at times not plentiful. As a result the length of the larval instars 

 may vary considerably, depending upon the food supply, tempera- 

 ture, and the length of the growing or feeding season. 



The life history of different species of Cicindela as given by Shel- 

 ford (1908) for northern Illinois is of three types and is as follows: 



(a) Eggs laid in late spring or early summer, larvae hibernate usually in 

 the third "stage, pupate in the second summer ; imagoes emerge about a month 

 after pupation, hibernate, and become sexually mature late in the third 

 spring— larval life lasts 12 to 13 months, adult life 10 months— two years be- 

 tween generations. 



(b) Eggs laid in mid summer, larvae hibernate usually in the third stage, 

 pupate in" the following June ; imagoes emerge in early July and become sexu- 



