340 



INSECTA. 



thredo is also furnished with a back ; but the groove is in the plate, and 

 receives a prominent ridge of the back, which is not fixed (to the saw). 



Fig. 171. 



Sirex gigas. 



but permits the saw to slide forward and backward as it is thrown out 

 and retracted. The saw of artificers is single ; but that of the Tenthredo 

 is double, and consists of two distinct saws with their backs : the insect, 

 in using them, first throws out one, and, while it is returning, pushes 

 forward the other ; this alternate motion is continued till the incision 

 is effected, when the two saws, receding from each other, conduct the 

 egg between them into its place." 



(892.) With respect to the number of eggs laid by insects, it varies 

 in different species : the Flea, for example, lays about twelve, and many 

 Diptera and Coleoptera average perhaps fifty ; but others are far more 

 prolific : among moths, for example, the Silkworm produces 500, and 

 some from 1000 to 2000 ; the Wasp ( Vespa vulgaris) deposits 3000 ; 

 the Ant (Formica), from 4000 to 5000. The Queen-bee is said by 

 Burmeister to lay from 5000 to 6000 ; but Kirby and Spence consider 

 that in one season the number may amount to 40,000 or 50,000, or 

 more. Yet, surprising as this latter statement may appear, the fecundity 

 of the Queen -bee is far inferior to that of the White Ant (Termes fatalis) ; 

 for the female of this insect extrudes from her enormous matrix innu- 

 merable eggs at the rate of sixty in a minute, which gives 3600 in an 

 hour, 86,400 in a day, and 2,419,200 in a lunar month. How long the 

 process of oviposition continues in the termite is unknown ; but if 

 it were prolonged through the entire year, the amazing number of 

 211,449,600 eggs would proceed from one individual ; setting, however, 

 the number as low as possible, it will exceed that produced by any 

 known animal in the creation. 



