58 Ohsei-vations on Insects affecting the Turnip Crops. 



/^ and black, excepting the scarlet wing-cases, and on the centre of 

 e"ach of them is a black dot ; at the inside of the eyes there is a 

 cream-coloured spot, and a larger one on each side of the thorax, 

 with two minute dots uniting at the base, of the same colour 

 (fig. 15). This insect is so variable in colour, and the individuals 

 are so very dissimilar, that it is called Coccinella dispar by many 

 authors, some specimens being blacky with a large red patch on 

 each shoulder, and a round spot of the same colour on each wing- 

 case, with the margin only of the eyes and of the thorax whitish ; 

 and between these extreme varieties will be found every gradation 

 from red to black : they are all about 2^ lines long. 



6. C. septempunctata, Linn. The seven -spotted lady-bird is 

 larger, very convex, being hemispherical, black, with bright brick- 

 red wing-cases, having a large black spot in the centre of the base, 

 with three smaller dots on each, forming a triangle : there are two 

 cream-coloured dots at the base of the head, and a large one at 

 each of the anterior angles of the thorax (fig. 16). It is more than 

 Sg lines long, and nearly 3 broad, and varies but little, the spots 

 sometimes being smaller than in our figure, and rarely vanishing. 



The next, perhaps, in importance amongst the parasites is a 

 diminutive fly (fig. 18), which hovers about plants infested by 

 the Aphides ; and the female soon settling amongst them, begins to 

 examine the herd with her vibrating horns, and having fixed on a 

 female Aphis, which is not already punctured, she bends down the 

 apex of her body, and pierces the insect with her ovipositor, which 

 is invisible to the naked eye : she then proceeds to another, de- 

 positing a single eg^ in each, and thus daily inoculates a consider- 

 able number. As the Aphis imbibes the juice of the plant, the 

 little maggot which has hatched in her body hourly increases in 

 size, growing with her growth, until the exhausted Aphis dies, 

 leaving its horny, shining, and inflated skin sticking by its rostrum 

 and legs to the plant, looking like a little tawny pearl : the parasite 

 then changes to a pupa, and, having completed its various trans- 

 formations, it becomes a perfect fly in about eight days, and eats 

 through the side of its cell, often leaving a round lid attached and 

 open like a door (fig. 17). 



These insects belong to the Order Hymenoptera, of the 

 Family Ichneumonides adsciti, and were described by 

 Linnaeus under the name of Ichneumon ajjhidum. The species I 

 have bred from the turnip aphides is now described as 



7. Aphidius (Trionyx) Rapse, Curtis * Antennae shorter than 

 the body, composed of fourteen joints, basal joint beneath, as well 

 as the mouth, ochraceous ; head and thorax shining black ; abdo- 



* Curtis's Brit. Ent., pi. 383, and the Guide Gen. 562 6 and 547, where 

 fifty-four British species of Aphidii are recorded, fornoing the subgenera 

 Praon, Ephedrus Toxares, Monoctonus, Trionyx^ and Aphidius of HaUday. 



