THE APHID^E. 141 



from the families already enumerated, we might sup- 

 pose that Asiraca or Lima would probably form part of 

 another great division, or that some of the lanigerous 

 genera, resembling Coccus, would here intervene ; but 

 we do not, at present, venture to act upon such vague 

 suspicion, and shall therefore leave this part of the series 

 for future investigation. 



(130.) Having now gone through the two typical 

 groups of the order Hemiptera, we shall at once 

 proceed to the three others, which appear to form the 

 aberrant divisions, namely, 1. the Aphides, or plant 

 suckers ; 2. the Coccides, or meal bugs ; and, 3. the 

 Aleyrodes. 



(131.) The APHIDES, or plant lice, as we have 

 already observed, are all of a very small, and often 

 minute, size, and live for the most part in societies. 

 Three of these families are represented by the Linnsean 

 genera Chermes, Aphis, and Thrips; while that of 

 Leach's Eriosoma is a type of the fourth. Of the 

 Chermes, we possess, comparatively, but few species ; 

 they are found on the leaves, young shoots, and bark of 

 different plants : in their larva state, they seem to ex- 

 hibit a considerable affinity to the Coccides, or plant 

 bugs ; and we think it is to that family, rather than to 

 this, that some of them really belong : like the Coccides, 

 many of them are coated, particularly towards the tail, 

 with a flocculent or cottony substance of a white colour, 

 and. of a clammy tenacious nature, which exudes from the 

 pores of the animal. These flocculent cotton-like fila- 

 ments are very conspicuous in the Chermes Alni 3 which 

 may be found, during summer, on the leaves and shoots 

 of the alder tree. The larva, as described by Dr. Shaw, 

 is entirely covered about the hinder part by thickly 

 fasciculated heaps of viscid down or cotton, which, if 

 purposely rubbed off, are quickly reproduced by the ani- 

 mal, which secretes the white fibres from large pores 

 placed in a circle at some distance from the vent. These 

 larvae, or grubs, are gregarious; often appearing in such 

 numbers on the tree, that the whole of the shoot they 



