Density and Parasitization of Grasshopper Egg-Pods in Pakistan

Abstract

A total of 1244 egg-pods of 12 grasshopper species were collected — 26.7% were from low altitude hills, 23% from Swat valley, 22.1% from Punjab plains, 19.4% from Peshawar region and 8.8% from Potohar plateau. Aiolopus thalassinus was the dominant species comprising 27.7% of the total pods. This was followed by Shirakiacris shirakli (24.5%), Oxya multidentata (13.6%), Trilophidia annulata (9.7%), Spathosternum prasiniferum (9.7%), Atractomorpha acutipennis(7.4%), Stenohippus sp. (3.8%) and Phlaeoba punteli (1.8%). Others were rare being less than 1%.

Egg-pod density was effected by several closely related factors. Mean annual temperatures (15.6–23.4°C) and average precipitation (310–2100 mm) of the localities were not the ultimate controlling factors. Parasitism however, appears to play an important role. Highest parasitism of Scelio spp. was 10% on the Potohar plateau where egg-pod population was lowest. A. thalassinus was the most preferred host(41.7%) followed by S. prasiniferum (35.4%), S. shirakii (14.6%), O. multidentata (8.3%), T. annulata and Stenohippus sp. (2.1% each). Soil-type (clay-loam, loam, sandy-loam) and type of vegetationl(cultivated area, grasslands) also have a considerable bearing on the microclimate in which the insects live.

Résumé

Un total de 1244 gousses, avec les pourcentages suivants: 26.7% des collines, 23% de la valley de Swat, 22.1% des plaines du Punjab, 195 de la region du Peshawar et 8.8% du plateau du Potohar, contenant des oeufs de 12 espèces de sauterelles a été collecté. L’ espèce dominante avec 27.7% du total des gousses fut Aiolopus thalassinus, suivit du Shirakiacris shirakii (24.5%), Oxya multidentata (13.6%), Trilophidia annulata (9.7%), Spathosternum prasiniferum (9.7%), Atractomorpha acutipennis (7.4%), Stenohippus sp. (3.8%) et Phlaeoba panteli (1.8%). Les autres espèces très rares n’ont pas fait 1%. La densité des gousses contenant des oeufs fut affecté par des différents facteurs. La moyenne annuelle des temperatures (15.6–23.4° C) et de pluviometrie (310–2100 mm) de ces localités n’étaient pas de facteurs de contrôle efficaces. Par ailleurs le parasitisme semble jouer un role important. Un parasitisme de 10% fut enregistre sur le plateau du Potohar la ou le nombre de gousses contenants des oeufs étaient très bas.