ISOTOMA. 171 



This is a variable species. The ground colour is 

 greenish-yellow, and there are three lines of dark, irre- 

 gular patches of brownish-purple ; one along the centre 

 of the back, and one on each side. In some specimens 

 the dark patches are large, and become almost 

 confluent ; the creature then appears brown, with two 

 irregular pale bands, and constitutes Bourlet's I. hifa- 

 sciata ; on the contrary, specimens in which the dark 

 parts are restricted form his I. trifasciata. Again, in 

 other specimens the dark parts are scarcely deeper in 

 colour than the rest of the body ; the intestinal canal 

 then appears through the skin, and this variety con- 

 stitutes, I believe, my I. lineata and Nicolet's I. riparia. 

 Nothing but the comparison of a long series of speci- 

 mens would have led me to regard insects which differ 

 so much at first sight, as forming only one species. 



That they do so, however, I have convinced myself, 

 and I am even inclined to doubt whether this species 

 is really distinct from the preceding. 



Sweden, Switzerland, France, England. 



Common in damp places, especially along the borders 

 of quiet ponds. 



The eggs, when first laid, are white, spherical, and 

 smooth. Those I have seen were laid in captivity 

 during the month of December. They were placed in 

 a small heap without any arrangement. 



Isotoma anglicana, Lubbock. 



Isotoma anglicana, Lubbock. Trans. Linn. Soc, 1862. 



Plate XXXVin. 



Colour purplish-greenish brown. Eyes on a black 

 patch. Under side of head and thorax the same 

 colour as the back, but slightly paler. Antennae con- 

 siderably longer than the head. Anterior abdominal 

 segments browner; saltatory appendage gradually 

 passing into white towards the extremities. A few 



