198 THE KNTOMOLOGIST. 



natum, Zett., var. ; humerale, Zett., var. ; dorsale, Zett., var. ; 

 meridionalis, Eamb., var. — Both this species and the next are 

 extremely variable, and some authors have described many of 

 the varieties as different species ; but there are only two, which 

 are easily distinguished by the comparative length of the pro- 

 thorax and abdomen. Common ; it occurs from April to October 

 in fields. 



2. T. hipunctata, L., 1761. = ohscura, Hagenb. ; nigricans, 

 Sow. ; laterale, Zett., var. ; vittatiim, Zett., var. ; binotatwm, 

 Zett., var. ; zonatum, Zett., var. ; ohsCiinim, Zett., var. ; ochra- 

 ceum, Zett., var.; hieroglypJiicum, Zett., var.; scriptum, Zett, 

 var. ; hilare, Zett., var. ; variegatmn, Zett., var. ; epliippimn, 

 Zett., var. ; carhonarium, Zett., var. ; pinnula, Curt., var. ; 

 scutdlatmn, DeGeer, var. — Comparatively shorter and broader 

 than T. suhulata ; it occurs from May to September in fields. 



[On page 175 in the first part of my article, Decticus griseus 

 was in error printed as "very local and rare "; it should have 

 been " local, but not rare."] 

 Dulwich Village, Surrey, May, 1889. 



ON THE VARIATION OF INSECTS. 



By T. D. a. Cookerell. 



(Continued from p. 178.) 



Class IV,— Variation in the Preparatory Stages.* 

 a. Larvce. 

 Contrary to what might have been expected, larvae vary greatly 

 without producing any corresponding variations in the perfect 

 insects arising from them ; while, on the other hand, the larvae 

 of an insect which is exceedingly variable in the perfect state may 

 be very constant in colouring, or if there are variations they may 

 have no relation to those hereafter to be observed in the imago. 

 It is, therefore, broadly speaking, impossible to associate the 

 variations seen in the different stages of insect growth together, 

 and larval variations must be treated, at least for the present, as 

 larval variations alone. In considering these variations, the first 

 thing that strikes us is the frequency of simple dichroism, usually 

 exhibited in green and brown forms, and the apparent spontaneity 

 of this variation without direct reference to external conditions 

 or hereditary influences. On further enquiry, however, we find 

 some striking cases in which the variation appears to be phyto- 

 phagic, and others in which it is of local distribution. The study 



* For lack of information about the larvic in other orders, I am obliged to 

 conline my remarka in this section entirely to Lepidoptera. 



