Vol. 9, Issue 8, Part I (2025)

The investigation into the biology of the Niger aphid, Uroleucon compositae, has revealed important insights into the developmental stages and morphological characteristics of this insect. The study found that the nymph of U. compositae goes through four distinct instars before reaching the adult stage. In the first nymphal instar, the aphid is wingless, elongated, delicate, and pale brownish in colour. It possesses small compound eyes located just behind the base of the antennae, which appear reddish to black. The first-instar nymph's measurements indicate a length of approximately 0.85±0.04 mm and a breadth of 0.36±0.03 mm. The antennae are relatively long, with five segments measuring about 0.88±0.05 mm. The three pairs of well-developed, light brown thoracic legs are uniformly covered with hairs, and their lengths are 0.688±0.005 mm (front), 0.824±0.007 mm (middle), and 0.950±0.020 mm (hind). The first instar nymphal period lasts for 2.43±0.67 days. In the second nymphal instar, the aphid darkens in colour, becoming dark brown, oval, and slightly bulged in shape. The compound eyes have three dot-like ommatidia at the posterior end. The nymph measures 1.22±0.06 mm in length and 0.56±0.03 mm in breadth. The antennae are shorter than the body, with five segments, and their length is 1.08±0.03 mm. The leg lengths are 0.885±0.014 mm (front), 0.972±0.024 mm (middle), and 1.196±0.023 mm (hind). Hairs are observed on all three pairs of legs, and the cornicles are distinct and cylindrical in shape. The second instar nymphal period lasts for 2.6±0.55 days. In the third nymphal instar, the aphid darkens further to a dark brown color. The compound eyes become larger, rounder, and reddish-black, and the antennae consist of six segments. The nymph's length is 1.55±0.12 mm, and its breadth is 0.77±0.06 mm. The antennal length measures 1.43±0.06 mm. The leg lengths are 0.983±0.030 mm (front), 1.165±0.010 mm (middle), and 1.912±0.028 mm (hind). The cornicles and cauda are dark brown. The duration of the third nymphal instar is 2.10±0.70 days. In the fourth nymphal instar, the aphid appears blackish in colour and elongated in shape. The compound eyes are expanded and remain black to reddish, and the antennae are six-segmented. The length and breadth of the fourth nymphal instar are 2.65±0.05 mm and 0.94±0.03 mm, respectively. The antennae measure 2.41±0.05 mm in length. The legs are stout, with the coxa, trochanter, distal area of the femur, and tibia being dark brown, while the remaining portions are light in color. The leg lengths are 1.524±0.043 mm (front), 1.815±0.063 mm (middle), and 2.353±0.106 mm (hind). The duration of the fourth instar is 2.30±0.64 days. The total nymphal period for U. compositae is 9.43±1.08 days. The adult aphid is shiny and dark black in colour, with a spindle-like to elongated pyriform body. The compound eyes are bulged and reddish-black. Alate adults are similar to apterous adults. The morphometrics of the adult reveal a length of 2.86±0.04 mm and a breadth of 1.25±0.03 mm. The antennae measure 2.68±0.02 mm in length, and the leg measurements are 2.222±0.076 mm (front), 2.328±0.032 mm (middle), and 2.897±0.099 mm (hind). The hind legs are particularly long and stout. The adult lifespan is 9.90±0.98 days. The adult life cycle consists of pre-reproduction, reproduction, and post-reproduction periods, which last for 1.13±0.76, 7.76±1.23, and 1.00±0.63 days, respectively. During the reproduction period, U. compositae exhibits a fecundity of 52.70±8.41 nymphs, and the total lifespan is 19.33±1.32 days.